urn  URES 


John  Swett 


Nature's  /BMraclee 


Familiar  Talks  on  Science 


BY 
ELISHA  GRAY,  PH.  D.,  LL.  D. 

U 


VOL.  I 

Bu(R>fn0  an&  Xife 
EARTH,  AIR,  AND  WATER 


NEW  YORK 
FORDS,  HOWARD,  &  HULBERT 


a.  i7i 

6-7 


COPYRIGHT,  1899, 

BY 
FORDS,  HOWARD  &  HULBERT. 

EDUCATION 


THE  MEESHON  COMPANY  PRESS, 
RAHWAY,  N.  J. 


CONTENTS. 


CHAPTER 

PAGE 

INTRODUCTION, 

V 

EARTH. 

I. 

WORLD  BUILDING  AND  LIFE,   . 

1 

II. 

12 

III. 

COAL,         

.      22 

IV. 

SLATE  AND  SHALE, 

.      31 

V. 

SALT,         

.      36 

AIR. 

VI. 

THE  ATMOSPHERE,    . 

.      42 

VII. 

AIR  TEMPERATURE, 

.      51 

VIII. 

CLOUD  FORMATION, 

.      60 

IX. 

CLOUD  FORMATION  (Continued], 

.      69 

X. 

WIND  —  WHY  IT  BLOWS, 

.      79 

XI. 

WIND  (Continued},    . 

.      88 

XII. 

LOCAL  WINDS, 

.     100 

XIII. 

WEATHER  PREDICTIONS, 

.     110 

XIV. 

How  DEW  Is  FORMED,     . 

.     115 

XV. 

HAILSTONES  AND  SNOW, 

.     124 

XVI. 

METEORS            .... 

129 

XVII. 

THE  SKY  AND  ITS  COLOR, 

.     134 

XVIII. 

146 

iii 

£434  43 


IV 


Contents* 


WATER. 
XIX.     RIVERS  AND  FLOODS,     .        .        .152 

XX.    TIDES, 161 

XXI.     WHAT  Is  A  SPONGE  ?     .        .        .167 
XXII.    WATER  AND  ICE,  .        .        .177 

XXIII.  STORED  ENERGY  IN  WATER,         .    182 

XXIV.  WHY  DOES  ICE  FLOAT  ?        .        .192 
XXV.    GLACIERS,       .        .        .        .        .198 

XXVI.    EVIDENCES  AND  THEORIES  OF  AN 

ICE  AGE, 207 

XXVII.    GLACIAL  AND  PREGLACIAL  LAKES 

AND  RIVERS,       .        .        .        .217 
XXVIII.     SOME  EFFECTS  OF  THE    GLACIAL 

PERIOD, 230 

XXIX.    DRAINAGE  BEFORE  THE  ICE  AGE,      239 


INTRODUCTION. 


Dear  Reader :  Please  look  through  this  "  In- 
troduction "  before  beginning  with  the  regular 
chapters.  It  is  always  well  to  know  the  object, 
aim,  and  mode  of  treatment  of  a  book  before 
reading  it,  so  as  to  be  able  to  look  at  it  from 
the  author's  view-point. 

First:  A  word  about  the  title — "Nature's 
Miracles."  Some  may  claim  that  it  is  un- 
scientific to  speak  of  the  operations  of  nature 
as  "  miracles."  But  the  point  of  the  title  lies 
in  the  paradox  of  finding  so  many  wonderful 
things — as  wonderful  as  any  miracle  that  was 
ever  recorded — subservient  to  the  rule  of  law. 

"  But,"  you  say,  "  a  miracle  does  not  come 
under  any  rule  of  law." 

Ah!  are  you  sure  of  that?  It  is  true  that 
we  may  not  understand  the  law  that  the  so- 
called  miracle  comes  under,  but  the  Author  of 
all  natural  law  does.  We  do  not  pretend  to 
dispute  but  that  the  Power  that  made  nature's 
laws  can  change  them  if  He  sees  fit;  but  we 
cannot  believe  that  He  will  ever  see  fit.  It 
would  destroy  all  order  and  harmony,  all  ad- 


vi  Unti'oDuctfom 

vancement  in  science  and  knowledge  of  God's 
works,  not  to  be  able  to  rely  implicitly  upon 
the  laws  of  nature  as  consistent  and  con- 
tinuous. 

In  putting  out  these  little  volumes,  it  is  not 
to  be  understood  that  the  subjects  treated  will 
be  more  than  touched  upon,  at  the  most  salient 
points.  To  do  much  more  would  require 
volumes  of  immense  size,  and  life  would  be  too 
short  for  me  to  write  or  for  you  to  read  them. 

Again :  these  volumes  are  "  familiar  talks." 
The  Author  wishes  to  sit  down  with  you — so 
to  speak — and  not  hold  you  at  arm's  length. 

It  will  be  his  aim  to  use  the  language  of 
common  life  and  to  avoid  all  technical  names 
so  far  as  possible,  or,  when  they  are  necessary, 
to  explain  their  meaning.  The  object  is  to 
reach  the  thousands  of  readers  who  have  not 
and  cannot  have  the  advantages  of  a  scientific 
education,  but  who  can  by  this  means  get  at 
least  a  rudimentary  idea  of  some  of  the  nat- 
ural laws  with  which  they  are  coming  in  con- 
tact every  hour,  and  through  which  the  inner 
man  has  constant  communication  with  the 
outer  world.  It  may  be,  too,  that  many  young 
students  will  be  helped  by  these  plain  general 
views  of  topics  which  their  text-books  will 
give  them  in  detail. 

A  knowledge  of  the  real  things  in  the  ob- 
jective world  about  us  and  the  laws  that  gov- 
ern them  in  their  inter-relations  is  of  practical 


ITntroDuctiom  vn 

value  to  every  man,  whatever  his  calling  may 
be.  Not  only  will  it  be  of  value  practically, 
but  it  will  also  be  a  constant  source  of  interest 
and  pleasure.  Man  is  so  constituted  that  he 
must  have  something  to  be  interested  in,  and 
if  he  has  no  resources  within  himself  he  looks 
elsewhere,  and  often  to  his  hurt,  mentally, 
morally,  or  otherwise.  If  he  could  have  an 
interest  awakened  in  him  for  the  study  and 
contemplation  of  the  natural  world  he  would 
then  have  a  book  to  read  that  is  always  open, 
always  fresh,  always  new.  He  is  dealing  with 
facts  and  not  theory,  except  as  he  uses  theory 
for  getting  at  facts. 

A  man  who  is  all  theory  is  like  "a  rudder- 
less ship  on  a  shoreless  sea."  All  he  really 
knows  is  that  he  is  afloat,  and  if  he  lands  at 
all  it  is  likely  to  be  in  an  insane  asylum.  The 
mind,  in  order  to  keep  its  balance,  must  have 
the  solid  foundation  of  real  things.  Theories 
and  speculations  may  be  indulged  in  with 
safety  only  so  long  as  they  are  based  on  facts 
that  we  can  go  back  to  at  all  times  and  know 
that  we  are  on  solid  ground. 

It  is  the  desire  and  aim  of  all  good  men  to 
make  their  nation  a  truly  great  people,  with 
a  civilization  the  highest  possible.  The  char- 
acter of  all  kinds  of  growth  is  largely  deter- 
mined by  the  character  of  the  material  upon 
which  it  feeds.  The  study  of  natural  law  can 
never  be  harmful,  but  is  always  beneficial,  for 


vni  Introduction, 

the  student  is  then  working  in  harmony  with 
law.  It  is  the  violation  of  law  that  makes  all 
the  trouble  in  the  world — whether  physical, 
moral,  or  social.  When  we  speak  of  natural 
law  we  do  not  confine  ourselves  to  what  is 
commonly  known  as  chemistry  and  physics, 
and  the  laws  that  govern  the  material  world, 
but  include  as  well  the  laws  of  our  own  being, 
as  intellectual  and  spiritual  units.  For  all 
law,  physical,  intellectual,  and  spiritual,  is  in 
a  sense  natural. 

All  departments  of  science  are  simply 
branches  of  one  great  science,  and  all  phases 
of  human  activity  are  touched  by  it.  The 
preacher  is  a  better  preacher,  the  doctor  a  bet- 
ter doctor,  the  lawyer  a  better  lawyer,  the  edi- 
tor a  better  editor,  the  business  man  a  better 
merchant,  and  the  mechanic  a  better  workman, 
if  they  follow  scientific  methods.  Indeed,  any 
man  will  be  a  better  husband,  father,  and  citi- 
zen, if  he  has  some  trustworthy  knowledge  of 
the  laws  under  which  this  great  universe,  down 
to  his  own  little  part  of  it,  lives,  moves,  and 
has  its  being. 


NATURE'S  MIRACLES. 


EARTH. 


CHAPTER  I. 

WORLD-BUILDING    AND    LIFE. 

"  In  the  beginning  God  created  the  heaven 
and  the  earth.  And  the  earth  was  without 
form,  and  void." 

Whatever  our  speculations  may  be  in  regard 
to  a  "  beginning,"  and  when  it  was,  it  is  writ- 
ten in  the  rocks,  that,  like  the  animals  and 
plants  upon  its  surface,  the  earth  itself  grew; 
that  for  countless  ages,  measured  by  years  that 
no  man  can  number,  the  earth  has  been  gradu- 
ally assuming  its  present  form  and  composi- 
tion, and  that  the  processes  of  growth  and  de- 
cay are  active  every  hour. 

The  science  that  deals  with  the  formations 
anl  stratifications  that  are  found  on  the  earth 
and  under  the  earth,  and  all  the  forces  that 
have  been  and  are  now  active  in  their  forma- 
tion, is  called  Geology  (earth  science).  It  is 
a  science  about  which  little  is  known  by  the 


lftature'0  /BMracles. 

average  individual,  and  yet  it  is  one  of  tran- 
scendent interest,  from  the  study  of  which  tha 
lover  of  nature  can  obtain  a  vast  amount  of 
profit  and  pleasure.  When  the  uncultured 
man  sees  a  stone  in  the  road  it  tells  him  no 
story  other  than  the  fact  that  he  sees  a  stone 
and  that  it  would  better  be  removed;  and  all 
the  satisfaction  he  gets  out  of  it  is  in  the 
thought  that  he  has  saved  some  unlucky  wagon 
wheel  from  being  wrenched  or  broken.  The 
scientist  looking  at  the  same  stone  perhaps 
will  stop,  and  with  a  hammer  break  it  open, 
when  the  newly  exposed  faces  of  the  rock  will 
have  written  upon  them  a  history  that  is  as 
real  to  him  as  the  printed  page.  He  is  carried 
back  to  a  far-off  time,  where  he  sees  the 
processes  and  forces  at  work  that  have  formed 
this  stone  and  made  it  what  it  is,  not  only  in 
its  outward  form,  but  in  its  constitution,  down 
to  its  molecules  and  atoms.  (The  word  "atom" 
is  used  in  chemistry  to  mean  the  smallest  par- 
ticle of  an  elementary  substance  that  will  com- 
bine with  the  atoms  of  another  substance  to 
form  new  compounds  of  matter.  And  mole- 
cules are  made  up  of  atoms.)  The  scientist 
looking  at  this  stone  sees  in  it  not  only  that 
mechanical  and  chemical  agencies  have  co- 
operated in  the  work  of  its  formation,  but  that 
animal  life  itself  may  have  been  the  chief 
agency  in  bringing  the  materials  together  and 
giving  form  to  the  peculiar  architecture  em- 


ant)  Xife, 

ployed  in  its  formation.  If  it  is  a  piece  of 
limestone  this  latter  statement  will  be  emi- 
nently true. 

Here  is  a  powerful  motive  for  the  study  of 
physical  science.  It  is  not  to  be  expected,  nor 
is  it  possible,  that  every  individual  can  be  a 
scientist  in  the  strict  sense  of  the  word,  but  it 
is  possible  for  everyone  of  ordinary  intelli- 
gence to  become  familiar  with  the  salient  facts 
of  science,  if  only  a  small  portion  of  the  time 
that  is  now  devoted  to  the  reading  of  litera- 
ture that  is  rather  harmful  than  helpful  be 
spent  in  studying  the  phenomena  and  works 
of  nature. 

The  acquirement  of  such  knowledge  would 
furnish  every  individual  with  a  constant 
source  of  instructive  amusement  that  would 
never  lose  its  interest.  He  would  not  be  de- 
pendent every  hour  upon  people  and  things 
outside  of  himself;  because  he  would  carry 
about  with  him  inexhaustible  sources  of  in- 
struction and  pleasure  that  would  furnish  him 
continual  and  helpful  diversion  and  save  him 
from  a  thousand  morbid  tendencies  that  are 
always  ready  to  seize  upon  an  unemployed 
mind.  There  are  many  men  and  women  in 
the  insane  asylum  to-day  for  the  simple  reason 
that  they  have  not  made  intelligent  use  of  the 
mental  powers  that  nature  has  endowed  them 
with. 

Sermons  are  not  always  preached  from  pul- 


IRature'0 

pits.  They  are  written  in  the  rocks  and  on 
the  flowers  of  the  field  and  the  trees  of  the 
forest. 

Let  us  then  look  a  little  at  the  underground 
foundation  of  all  this  beautiful  earth.  And 
before  attempting  that,  the  question  may  arise 
in  some  minds  how  we  know  what  is  so  deep 
down  under  the  surface.  Fortunately  this  is 
a  question  very  easily  answered.  At  some 
period  after  the  rocks  were  formed  the  crust 
of  the  earth  was  broken  by  volcanic  eruptions 
at  various  places  and  times,  and  turned  up,  as 
in  the  formation  of  mountains,  so  that  the 
edges  of  the  various  stratifications  of  the 
rocks,  from  those  near  the  surface  down  to  the 
lowest  rocks,  are  exposed  to  view.  Another 
means  of  knowing  what  the  various  forma- 
tions are  has  been  by  borings  of  deep  wells. 
These  borings,  however,  are  only  confirmatory 
of  what  was  well  known  before  through  the 
upheavals  that  are  plentiful  in  all  parts  of  the 
world.  There  is  abundant  evidence  that  all 
of  the  rocks  and  all  of  the  strata  of  every  name 
and  nature  (except  perhaps  igneous  rocks) 
were  originally  laid  down  in  water.  This  is 
evidenced  not  only  by  the  stratifications  them- 
selves, but  by  the  evidences  of  sea-life  every- 
where present  in  the  earth's  crust.  Before 
the  upheavals  in  the  earth's  crust  began,  the 
whole  surface  of  the  globe  was  a  great  ocean 
of  hot  water.  The  substances  of  which  the 


rocks  were  formed  were  undoubtedly  held  in 
suspension  in  the  air  and  in  the  water,  and  by 
a  gradual  process  were  deposited  in  the  bottom 
of  the  ocean  in  layers,  forming  rocks  of  vari- 
ous kinds,  according  to  the  nature  of  the  sub- 
stance deposited.  Gradually  the  crust  of  the 
earth  was  built  up  until  it  acquired  a  certain 
thickness;  when,  either  from  shrinkage  under 
the  crust  a  great  void  was  formed  until  it  could 
not  sustain  its  own  weight,  or  the  pressure 
caused  by  confined  gases  and  molten  matter 
produced  an  upheaval  which  broke  the  crust 
of  the  earth  outward,  causing  great  wrinkles 
that  we  call  mountain  ranges.  Undoubtedly 
both  forces  were  active  in  producing  these  re- 
sults. When  the  gases  and-  molten  matter  had 
escaped  through  the  rifts  in  the  rocks  caused 
by  the  upheaval  there  must  have  been  great 
voids  formed  that  were  filled  up  by  the  shrink- 
age of  the  earth,  causing  much  irregularity  in 
its  surface. 

In  some  places  there  were  enormous  eleva- 
tions, and  in  others  correspondingly  deep  de- 
pressions. The  water  that  before  was  evenly 
distributed  over  the  surface  of  the  globe,  after 
the  upheavals  ran  off  into  the  lower  levels,  fill- 
ing up  the  great  valleys,  forming  the  seas,  and 
leaving  about  one-third  of  the  land  surface 
uncovered.  It  must  not  be  supposed,  however, 
that  the  appearance  of  the  land  was  caused  by 
one  grand  movement  or  upheaval,  but  that  it 


6  fiature's 

has  been  going  on  in  successive  stages  through 
long  ages  of  time.  This  is  clearly  evidenced 
by  the  rock  formations.  The  deposition  of 
rock  strata  is  still  active  in  the  bottoms  of  the 
oceans,  although  not  to  the  same  degree  as  in 
former  times.  When  the  upheaval  took  place 
the  old  stratifications  were  thrown  out  of  level, 
but  the  new  ones  that  were  then  formed  re- 
mained in  a  level  position  until  they  were  in 
their  turn  disturbed  by  some  subsequent  up- 
heaval. 

The  laws  of  gravitation  would  tend  to  pre- 
cipitate the  matter  held  in  suspension  by  the 
water  straight  down  to  the  bottom,  toward  the 
center  of  the  earth,  so  that  the  plane  of  these 
stratifications  would  tend  to  be  parallel  to  the 
surface  of  the  water,  that  is  horizontal,  until 
disturbed.  Then  they  would  be  tilted  in  many 
directions.  Hence  it  will  be  easily  seen  why 
the  seams  in  the  rocks,  especially  in  and  near 
mountainous  regions,  do  not  lie  in  a  horizontal 
position  after  an  upheaval,  but  are  found 
standing  at  all  angles,  up  to  a  perpendicular. 

Viewed  from  this  standpoint,  the  solid  por- 
tion of  the  old  world  has  gone  all  to  pieces. 
Wherever  there  is  a  chain  of  mountains  it 
marks  a  breakage  in  the  earth's  crust,  and 
these  mountains  are  not  all  on  the  land,  but 
extend  under  the  seas  so  deeply  that  they  are 
unable  to  lift  their  heads  above  the  surface  of 
the  water.  The  earth  is  no  longer  round,  ex- 


!lLife>  1 

cept  in  general  outline,  but  broken  up  into  all 
sorts  of  shapes  that  give  the  varied  conditions 
of  landscape  that  we  find  whichever  way  we 
turn. 

There  are  but  few  volcanoes  that  are  active 
in  this  age,  while  in  former  times  they  ex- 
tended for  thousands  of  miles.  We  still  have 
occasional  earthquakes,  but  undoubtedly  they 
are  very  slight  as  compared  with  those  that 
shook  the  earth  millions  of  years  ago. 

If,  now,  we  study  the  constitution  of  the 
earth's  crust  so  far  as  it  has  yet  been  pene- 
trated, we  find  it  divided  up  into  periods  called 
Primary,  Secondary,  and  Tertiary.  The  pri- 
mary period  reaches  down  to  the  line  where 
the  lowest  forms  of  animal  fossils  begin  to  be 
found.  This  is  called  the  "  Paleozoic  "  period, 
which  means  the  period  of  "  ancient  life." 
From  here  let  us  first  go  downward.  Im- 
mediately under  this  lies  a  stratum  of  "  Meta- 
morphic "  rocks.  To  metamorphose  is  to 
change;  and  metamorphic  rocks  are  those 
which  have  been  changed  by  heat  or  pressure 
from  their  original  formation.  This  class  of 
rocks  lie  on  top  of  what  are  called  "  Igneous  " 
rocks,  which  means  that  they  have  been 
formed  by  or  subjected  to  heat.  All  lava- 
formed  rocks  are  igneous.  They  are  unstrati- 
fied, — not  in  layers  or  strata,  but  in  a  formless 
mass, — and  in  this  they  differ  from  water- 
formed  rocks. 


8  Nature's 

If  there  is  a  molten  center  to  the  earth  these 
igneous  rocks  are  undoubtedly  the  offspring 
of  this  great  internal  furnace.  The  meta- 
morphic  rocks  were  primarily  igneous  and  are 
changed  somewhat  in  their  structure  by  the 
lapse  of  time.  For  instance,  marble  is  a  meta- 
morphic  limestone.  The  difference  between 
common  limestone  and  marble  is  in  its  molec- 
ular structure — the  way  in  which  its  smallest 
particles  are  put  together.  They  are  both 
carbonates  of  lime.  But  the  marble  is  made 
up  of  little  crystals  and  will  take  a  polish, 
while  ordinary  uncrystallized  limestone  will 
not.  The  igneous  rocks  are  chiefly  granite; 
and  granite  is  formed  of  orthoclase-feldspar, 
mica,  and  quartz.  (The  word  "  orthoclase " 
means  straight  fracture,  and  the  orthoclase- 
feldspar  has  two  lines  of  cleavage  at  right 
angles  to  each  other.)  This  is  the  ordinary 
composition  of  granite,  but  there  are  a  great 
many  variations,  chiefly  as  to  color  and  pro- 
portions of  the  ingredients  named. 

The  igneous  rocks,  then,  are  the  lowest  of 
all;  then  come  the  metamorphic  rocks;  and 
as  before  stated,  on  top  of  metamorphic 
rock  begins  the  first  evidence  of  life  in  its 
lowest  form.  The  Paleozoic  (ancient  life)  or 
Primary  period  is  made  up  of  a  number  of 
subdivisions.  The  first  and  oldest  division  is 
called  the  "  Silurian  "  age,  which  is  underlaid 
by  the  metamorphic  rocks  and  overlaid  by  the 


anfc  Kite.  9 

rocks  of  the  Devonian  period.  It  is  called 
Silurian,  from  the  name  of  a  kind  of  fish,  fos- 
sils of  which  are  found  in  the  rocks  of  this 
age,  which  are  distinguished  for  the  absence  of 
land-plant  fossils  and  vertebrate  animals. 

In  i;he  Silurian  strata  are  found  limestones, 
slate, 'flagstones,  shales,  etc.  On  top  of  the  Si- 
lurian begins  the  "  Devonian "  age,  in  which 
is  found  the  old  red  sandstone,  as  well  as  lime- 
stone and  slate;  and  here  begin  to  be  found 
the  fossils  of  land-plants.  On  top  of  the  De- 
vonian lies  the  "  Carboniferous  "  series,  which 
complete  the  series  of  the  primary  period.  In 
the  lower  part  of  this  stratum  is  found  car- 
boniferous limestone,  which  is  overlaid  by  a 
kind  of  stone  called  millstone  grit,  and  on  top 
of  this  lie  the  true  carboniferous  strata  or 
coal-bearing  measures.  In  the  coal  strata  are 
found  the  first  reptile  fossils. 

On  top  of  the  coal  measures  begins  the  Sec- 
ondary period,  or  "  Mesozoic  "  (middle  life). 
This  period  is  distinguished  for  the  great  de- 
velopment of  reptiles,  and  is  called  the  "  age 
of  reptiles."  In  this  age  occur  the  first  traces 
of  mammals,  and  birds,  and  fishes  with  bony 
skeletons.  Among  plants  we  find  here  the 
first  evidence  of  palms.  The  formation  is 
chiefly  chalk,  sandstones,  clays,  limestone,  etc. 
We  now  come  to  the  last  or  "  Tertiary  "  period, 
which  brings  us  to  the  top  earth.  This  is 
chiefly  formed  of  sedimentary  rocks — those 


10  IKature'0  .Miracles. 

which  have  been  formed  by  the  settling  of 
sediment,  in  water. 

While  we  are  forced  to  these  general  conclu- 
sions in  regard  to  the  building  of  the  world, 
and  to  its  subsequent  distortion  by  the  series 
of  upheavals  that  have  occurred  from  time  to 
time, and  to  the  successive  "ages"  of  the  layers 
of  rock  foundation  of  its  crust,  there  are  many 
mysteries  that  remain  unsolved  and  many 
questions  will  present  themselves  to  the  mind 
of  the  reader.  One  of  these  questions  is, 
Where  was  the  water  and  where  was  the  earthy 
matter  before  its  precipitation?  Matter,  in- 
cluding water,  can  exist  in  the  gaseous  form, 
and  we  only  need  to  assume  that  there  was  a 
core  of  intense  heat,  to  understand  how  all 
the  material  that  we  find  on  the  earth  and  in 
the  earth  could  have  been  held  in  suspension 
in  the  gaseous  state  until  the  cooling  process 
had  reached  a  stage  where  the  various  combi- 
nations and  recombinations  could  take  place 
in  the  great  laboratory  of  nature.  If  we  study 
the  constitution  of  the  sun  (and  with  the 
modern  appliances  we  are  able  to  do  so),  we 
find  that  it  is  made  up  of  some  and  perhaps  all 
of  the  same  materials  that  are  found  here  on 
earth.  If  there  is  no  water  existing,  in  the 
sun,  as  water,  there  are  the  gases  present 
which  would  produce  it  if  the  conditions  were 
right.  And,  for  all  we  know,  that  flaming 
mass  of  burning  gases  may  some  time  go 


anfc 

through  the  same  kind  of  cooling  and  build- 
ing up  in  solids  that  our  earth  has  experi- 
enced. 

We  thus  have  what  may  be  called  an  outline 
sketch  of  the  process  of  World-building. 


CHAPTEK  II. 

LIMESTONE. 

A  large  part  of  the  structure  of  the  earth's 
crust  is  formed  of  a  substance  called  lime- 
stone. Ordinary  limestone  is  a  compound  of 
common  lime  and  carbon  dioxide,  a  gas  that  is 
found  mixed  with  the  air  to  a  very  small  de- 
gree. Carbon  dioxide  will  be  better  known  by 
the  older  people  as  carbonic  acid.  It  is  a  gas 
that  is  given  off  whenever  wood  and  coal  are 
burned,  or  any  substance  containing  carbon. 
It  is  composed  of  one  atom  of  carbon  to  two  of 
oxygen.  Every  ton  of  coal  that  is  burned 
sends  off  three  and  two-thirds  tons  of  this  gas. 
The  increase  in  weight  comes  from  the  fact 
that  every  atom  of  carbon  unites  with  two  of 
oxygen,  which  it  takes  from  the  air,  and  the 
oxygen  is  heavier  than  the  carbon. 

In  comparing  the  relative  weights  of  atoms 
(the  smallest  combinable  particle  of  a  solid, 
liquid,  or  gas)  we  use  the  hydrogen  atom  as 
the  unit  of  comparison  and  call  it  "  one,"  be- 
cause it  is  the  lightest  of  all  atoms.  The  car- 
is 


3Llme0tcme.  13 

bon  atom  is  twelve  times  heavier  than  the  hy- 
drogen atom,  and  the  oxygen  atom  is  sixteen 
times  heavier.  Hence  it  will  be  seen  readily 
how  a  ton  of  coal  will  form  two  and  two-thirds 
times  its  weight  of  carbonic  dioxide.  Lime, 
having  a  strong  affinity  or  attraction  for  this 
gas,  has  absorbed  it  from  the  air  and  water, 
forming  what  is  known  as  carbonate  of  lime — 
which  is  the  ordinary  limestone.  Chalk  and 
the  various  marbles  are  also  carbonates  of 
lime.  Limestone  strata  in  the  crust  of  the 
earth  are  found  in  all  the  periods  of  the 
earth's  formation.  All  forms  of  sea  shells 
that  were  once  the  homes  of  animal  life  are 
constructed  of  this  compound ;  and  in  the  later 
formations  of  limestone,  in  the  Secondary  and 
Tertiary  periods,  we  find  this  rock  to  be  made 
up  almost  entirely  of  marine  shells,  some  of 
them  microscopic  in  size.  The  earlier  or  older 
formations  of  limestone  that  are  found  deeper 
down  in  the  earth's  crust  are  less  mingled  with 
these  marine  shells.  This  comes  from  the  fact 
that  the  first  deposition  of  limestone  strata 
occurred  before  the  later  forms  of  sea  life  had 
developed.  Whatever  signs  of  life  are  found 
in  these  lower  stratifications  are  of  the  very 
lowest  order.  It  is  not  to  be  understood  that 
animal  life  is  a  necessary  factor  in  the  forma- 
tion of  limestone,  but  it  has  been  an  inciden- 
tal feature  which  no  doubt  has  been  the 
chief  means  of  gathering  up  from  the  water 


14  maturc'6  /HMraclee. 

this  compound  and  precipitating  it  into  the 
great  limestone  strata  that  are  everywhere 
found. 

Carbonate  of  lime  is  found  in  solution  in 
nearly,  if  not  quite,  all  of  the  mineral  waters, 
and  is  also  found  in  the  water  of  the  ocean. 
In  earlier  times  it  must  have  been  held  in  so- 
lution in  much  greater  quantities  than  at  pres- 
ent. The  myriads  of  sea  animals  that  existed, 
and  that  still  exist,  gathered  from  the  water 
this  substance,  which  formed  their  shells,  and 
served  as  a  house  in  which  they  lived.  New 
germs  were  continually  forming  new  shells, 
while  the  older  ones  ceased  to  live  as  animals, 
and  their  houses  in  which  they  lived  were  pre- 
cipitated to  the  bottom  of  the  ocean,  where 
they  were  bound  together  as  limestone  rock. 
These  sea  animals  no  doubt  caused  a  much 
more  rapid  formation  of  limestone  than  would 
or  could  have  been  the  case  without  their 
existence. 

One  can  thus  readily  see  what  an  important 
factor  animal  life  has  been  in  the  process  of 
world-building.  This  process  is  still  going  on, 
but  probably  not  to  the  same  extent  as  in  for- 
mer ages,  because  it  is  not  likely  that  there  is 
so  much  carbonate  of  lime  held  in  solution  as 
there  was  before  these  great  limestone  beds 
were  formed.  Limestone,  however,  is  easily 
disintegrated  by  the  action  of  water.  We  find 
the  spring  water  impregnated  with  it  as  well 


Itimestone.  15 

as  that  of  the  small  streams  and  rivers.  Pure 
water  is  a  powerful  solvent.  When  the  rains 
fall  upon  the  earth  the  water  percolates 
through  it  and  through  the  limestone  strata, 
which  gradually  wears  away  the  limestone  and 
carries  it  back  to  the  ocean,  so  that  the  process 
of  tearing  down  and  building  up  is  continually 
going  on.  The  great  caves  that  are  found 
everywhere  in  the  limestone  regions  were 
formed  by  the  action  of  water.  The  great 
Mammoth  Cave  of  Kentucky,  which  is  said  to 
have  200  miles  of  underground  passages,  has 
been  entirely  worn  out  by  the  action  of  run- 
ning water. 

Some  years  ago  the  writer  visited  this  cave 
and  had  an  opportunity  to  study  the  wonder- 
ful eroding  or  gnawing-out  effect  of  water  on 
limestone.  At  some  period  earlier  in  the  his- 
tory of  the  earth  there  was  evidently  an  under- 
ground river  or  large  stream  of  water  that 
found  its  way  through  the  crevices  of  the 
rocks,  and  gradually  wore  out  a  great  bed  for 
itself,  which  was  fed  by  lateral  streams  pour- 
ing into  the  main  branch,  each  one  of  which 
lateral  branches  cut  its  own  channel.  A  plan 
view  of  the  Mammoth  Cave  presents  a  picture 
not  unlike  that  of  a  great  river  with  numerous 
branches  emptying  into  it,  all  of  them  showing 
the  windings  such  as  we  see  in  a  river  and  its 
feeders  upon  the  surface  of  the  earth.  There 
are  three  sets  of  these  channels,  one  above  the 


16  1ftature'0 

other,  and  we  do  not  find  the  water  till  we  get 
to  the  bottom  of  the  third  underground  story, 
so  to  speak.  There  is  one  place  in  this  system 
of  underground  channels  where  the  dripping 
from  the  roof  of  the  upper  channels  has  cut  a 
great  well  hole  many  feet  in  diameter  perpen- 
dicularly down  through  the  whole  system  to  a 
great  depth.  The  sides  of  this  great  well  hole 
are  fluted  into  grooves  caused  by  the  constant 
downflow  of  the  water.  Although  the  amount 
of  water  flowing  down  through  this  well  hole 
is  very  small,  it  is  continually  at  work.  Like 
interest  on  money,  it  never  rests,  each  minute 
that  passes  has  eaten  away  some  of  the  great 
rock. 

In  other  portions  of  the  cave  the  dripping  of 
the  water  is  so  gradual  that  the  carbonate  of 
lime  hardens  and  forms  what  are  called  stal- 
actites, that  hang  like  icicles  from  the  roof  of 
the  cave.  Sometimes  the  water  runs  down  so 
slowly  upon  these  stalactites  that  it  evaporates 
as  fast  as  it  appears,  leaving  behind  its  little 
load  of  carbonate  of  lime.  If,  however,  there 
is  a  drip,  there  are  formations  built  also 
from  the  lime  in  the  dropping  water  on  the 
floor  of  the  cave,  and  these  are  called  stal- 
agmites. In  time  the  stalactites  and  the 
stalagmites  will  meet,  forming  a  great  column 
reaching  from  floor  to  ceiling.  Some  of  these 
formations,  when  they  are  free  from  foreign 
substances,  are  very  beautiful.  They  are  also 


Ximeetone.  l* 

very  hard,  giving  off  a  metallic  musical  tone 
when  struck  by  any  hard  substance. 

We  have  already  stated  that  limestone  is  a 
compound  of  ordinary  lime  and  carbon  diox- 
ide, forming  a  carbonate  of  lime.  This  state- 
ment does  not  give  a  complete  analysis  of  all 
the  elements  entering  into  limestone.  In  the 
first  place  lime  itself  is  a  compound  formed 
of  two  elementary  substances,  calcium  and 
oxygen.  The  lime  molecule  is  composed  of 
one  atom  of  calcium  and  one  of  oxygen. 
Neither  calcium  nor  lime  is  found  pure  in 
nature.  Inasmuch  as  carbon  dioxide  is  com- 
posed of  one  atom  of  carbon  and  two  of 
oxygen,  and  lime  is  composed  of  one  atom  of 
calcium  and  one  of  oxygen,  when  we  have  the 
two  combined  the  molecule  of  carbonate  of 
lime,  or,  as  it  is  technically  called,  calcic  car- 
bonate, is  composed  of  one  atom  of  calcium, 
one  of  carbon  and  three  of  oxygen,  (lime  plus 
carbon  dioxide). 

As  before  stated,  lime  is  not  found  un-com- 
bined  with  other  substances  in  nature.  And 
as  it  is  of  great  economic  importance,  it  will 
be  profitable  to  know  how  it  is  formed.  Lime 
is  produced  from  ordinary  limestone  by  burn- 
ing it  in  kilns  where  it  is  subjected  to  a  heat 
of  a  certain  temperature  for  a  number  of 
hours.  The  heat  drives  off  the  carbon,  dioxide, 
which,  as  we  have  seen,  has  taken  away  from 
each  molecule  of  the  compound  all  of  the  car- 


18  Hature'0  Afracles. 

bon  and  two  atoms  of  the  oxygen,  while  all  of 
the  calcium  is  retained  with  one  atom  of  oxy- 
gen, leaving  ordinary  lime.  Lime,  then,  is 
simply  oxide  of  calcium. 

As  all  know,  it  is  used  almost  exclusively  for 
making  mortar  for  building  purposes.  In 
order  to  do  this  we  have  to  put  it  through  the 
process  of  "  slacking/'  by  pouring  water  upon 
it,  and  here  another  chemical  change  takes 
place.  The  water  unites  with  the  lime,  when 
immediately  the  heat  that  was  expended  iri 
throwing  off  the  carbon  dioxide  and  was  stored 
in  the  lime  as  energy  is  now  given  up  again  in 
the  form  of  heat.  When  a  considerable  bulk 
of  lime  is  slacked  very  rapidly  the  heat  that  is 
given  off  is  so  great  that  it  will  produce  com- 
bustion. Here  is  a  beautiful  illustration  of 
what  has  been  erroneously  called  "latent  heat." 
It  is  "  heat  stored  as  potential  energy,"  that  is 
released  by  the  combination  of  lime  with 
water.  Slackened  lime,  then,  is  called  calcic 
hydrate. 

Very  little  of  the  limestone  that  we  find  is 
absolutely  pure.  It  is  considered  good  when 
it  does  not  contain  over  five  or  six  per  cent,  of 
foreign  substance.  When  more  than  this  is 
present  the  lime  is  considered  poor,  and  when 
it  reaches  fifteen  per  cent,  or  more  of  impuri- 
ties it  assumes  the  property  of  hardening 
under  water  and  is  called  cement. 

Carbonate  of  lime  is  found  in  several  other 


Xtmeetone,  19 

forms;  for  instance,  the  various  kinds  of 
marble  and  chalk  are  carbonates  of  lime. 
The  composition  of  marble  and  chalk  is 
exactly  the  same  as  that  of  limestone.  The 
difference  is  chiefly  one  of  molecular 
rather  than  chemical  structure.  Marble 
is  what  chemists  would  call  an  allotropic 
or  changed  form  of  limestone;  and,  as  be- 
fore stated,  the  difference  seems  to  consist 
in  the  fact  that  the  marble  assumes  a  crys- 
talline arrangement  of  its  atoms  and  will 
therefore  take  a  high  polish,  which  is  not  true 
of  ordinary  limestone.  Marble  varies  greatly 
in  coloring  and  texture,  all  of  which  differ- 
ences are  explainable  under  the  one  head  of 
molecular  arrangement.  Nearly  pure  carbon 
exists  in  three  distinct  forms — the  diamond, 
graphite,  and  charcoal.  As  is  the  case  with 
marble,  these  differences  in  the  different  forms 
of  carbon  are  not  chemical,  but  molecular 
differences.  The  substances  are  the  same,  but 
their  infinitesimal  particles  are  differently  ar- 
ranged. 

Carbonate  of  lime — as  it  exists  in  its  vari- 
ous forms,  as  limestone,  from  which  lime  and 
cement  are  made,  and  marble,  which  is  such 
an  important  element  in  the  arts — is  a  sub- 
stance of  great  importance  to  man.  We  have 
already  noted  some  of  the  processes  that  nature 
uses  in  gathering  up  these  substances  from  the 
ocean  by  the  employment  of  various  forms  of 


20  lftature'0 

animal  life.  Here  is  another.  Whoever  has 
visited  the  Bermudas  has  seen  an  island 
wholly  formed  of  what  is  called  coral  rock. 
Coral  is  a  structure  produced  by  a  peculiar 
form  of  sea  animal  that  gathers  up  the  calca- 
reous or  lime-like  matter  floating  in  the  sea 
water,  and  builds  a  house  of  it  in  which  to  live 
during  the  little  lifetime  that  is  allotted  to 
him.  When  he  dies  his  children  do  not 
occupy  the  old  home,  but  build  a  new  one, 
which  is  a  superstructure  planted  upon  the  old 
one  as  a  foundation.  This  process  of  growth 
sometimes  takes  the  form  of  a  tree  or  plant, 
and  coral  trees  grow  upon  trees  and  plants 
upon  plants,  until  a  structure  is  erected  hav- 
ing its  foundation  upon  the  bottom  of  the 
ocean,  that  finally  reaches  up  until  it  rises 
above  the  surface  of  the  water;  and  here — 
after  through  years  the  water  has  brought  sea- 
weed and  drift  to  decay  and  form  soil,  and  the 
birds  have  brought  seeds  and  fertilization,  and 
vegetable  life  is  prospering — another  animal 
called  man  builds  his  home  upon  it.  The  ma- 
terial that  the  coral  is  formed  of  is  substan- 
tially the  same  as  that  we  find  in  the  minute 
shells  of  the  limestone  rocks. 

The  great  chalk  cliffs  that  are  found  on  the 
coasts  of  the  English  channel  are  the  work  of 
a  sea  animal  microscopic  in  size.  At  one 
time  it  was  a  question  among  scientists  how 
these  chalk  cliffs  were  formed,  but  when  the 


microscope  was  invented  this  mystery,  as  well 
as  many  others,  was  solved.  The  chemical 
components  of  chalk  are  precisely  the  same  as 
those  of  limestone.  The  microscope  shows 
that  chalk  is  almost  wholly  a  product  of  very 
small  organized  shells.  The  animals  who  are 
the  architects  of  the  chalk  cliffs  are  called 
"  f oraminif era  " — bearing  shells  perforated 
with  little  holes.  The  chief  difference  be- 
tween chalk  and  limestone  seems  to  be  in  the 
size  of  the  shells  of  which  they  are  respectively 
made  up  and  in  the  manner  of  the  bonding  of 
these  shells  together.  The  shells  in  a  lump  of 
chalk  are  held  much  more  loosely  than  those 
in  a  lump  of  limestone.  These  intrepid 
workers  are  still  actively  changing  the  struc- 
ture of  the  bottoms  of  seas  and  oceans,  and 
forming  new  islands,  which  in  turn  become  the 
substructure  that  supports  new  life,  animal 
and  vegetable.  And  when  we  consider  the 
great  part  performed  by  these  microscopic 
architects  and  builders  it  is  not  a  misnomer 
to  speak  of  the  building  of  a  world. 


CHAPTEE  III. 

COAL. 

Some  time,  long  ago,  some  man  made  the 
discovery  that  what  we  now  call  coal  would 
burn  and  produce  light  and  warmth.  Who  he 
was  or  how  long  ago  he  lived  we  do  not  know, 
but  as  all  earthly  things  have  a  beginning,  we 
know  that  such  a  man  did  live  and  that  the 
discovery  that  coal  would  burn  was  made. 
Coal,  in  the  sense  that  we  use  the  word  here, 
is  not  mentioned  in  the  Scriptures.  Accord- 
ing to  some  authorities,  coal  was  used  in  Eng- 
land as  early  as  the  ninth  century.  It  is  re- 
corded that  in  1259  King  Henry  III.  granted 
a  privilege  to  certain  parties  to  mine  coal  at 
Newcastle.  It  is  further  stated  that  seven 
years  after  this  time  coal  became  an  article  of 
export.  In  1306  coal  was  so  generally  used  in 
London  that  a  petition  was  sent  to  parliament 
to  have  the  use  of  it  suppressed  on  the 
ground  that  it  was  a  nuisance.  Coal  was 
used  in  Belgium,  however,  about  1200.  There 


Coal.  23 

is  a  tradition  that  a  blacksmith  first  used  it  in 
Liege  as  fuel.  It  was  first  used  for  manu- 
facturing purposes  about  1713. 

Coal  is  found  laid  down  in  great  veins, 
varying  in  thickness,  in  various  parts  of  the 
world  in  the  upper  strata  of  the  Paleozoic 
period.  The  age  in  which  it  was  formed  is 
called  by  geologists  the  Carboniferous  (coal- 
bearing)  age. 

Before  going  on  to  account  for  the  deposits 
of  coal,  let  us  stop  a  moment  and  consider 
what  it  is.  Chemists  tell  us  that  coal  is 
chiefly  constructed  of  carbon,  compounded 
with  oxygen,  hydrogen,  and  nitrogen.  There 
are  many  varieties,  but  all  may  be  classified 
under  two  general  headings — bituminous  and 
anthracite.  Bituminous  coal  contains  a  large 
amount  of  a  tarry  substance,  a  kind  of  mineral 
pitch  or  bitumen,  which  burns  with  a  brilliant 
flame  and  a  black  sooty  smoke,  exceedingly 
rich  in  carbon.  Anthracite  coal  is  hard  and 
stone-like  in  its  texture,  burning  with  scarcely 
any  flame  and  no  smoke.  It  produces  a  fire  of 
intense  heat  when  it  is  once  ignited.  There 
is  another  form  of  coal  called  cannel  coal, 
which  is  a  corruption  of  "candle  coal,"  so 
called  because  a  piece  of  this  kind  of  coal 
when  ignited  will  burn  like  a  match  or  pine 
knot  and  give  light  like  a  candle.  This  is  the 
richest  of  all  the  coal  deposits  in  gases  that  are 
set  free  by  heat,  and  for  this  reason  is  exten- 


24  matured  /HMracles* 

sively  used  in  the  manufacture  of  what  is  com- 
monly called  coal  gas.  England  produces  a 
large  amount  of  cannel  coal,  as  well  as  another 
variety  of  bituminous  coal,  which  latter, 
however,  does  not  burn  with  such  a  black 
smoke  as  the  coal  found  in  the  Ohio  valley  and 
the  Western  States  of  America.  East  of  the 
Alleghany  Mountains  there  is  a  region  of  an- 
thracite coal  that  is  very  extensively  worked 
and  finds  great  favor  in  all  parts  of  the  coun- 
try as  fuel  for  domestic  heating,  especially  on 
account  of  its  great  cleanliness. 

All  of  the  coal  beds  have  a  common  origin, 
and  the  difference  in  the  quality  of  coal  found 
in  different  parts  of  the  country  is  due  to 
many  circumstances,  some  of  which  have  never 
been  explained.  There  is  indisputable  proof, 
however,  that  all  coal  beds  are  of  vegetable 
origin.  Geologists  tell  us  that  these  coal  beds 
were  formed  during  an  age  before  the  earth 
had  cooled  down  to  the  temperature  that  it 
has  at  the  present  time — an  age  when  vegeta- 
tion was  forced  by  the  internal  heat  of  the 
earth  instead  of  having  to  receive  all  its 
warmth  from  the  sun's  rays  as  we  do  now. 
Some  of  our  readers  are  familiar  with  what  is 
commonly  termed  a  hotbed.  A  hotbed  is 
made  by  putting  soil  on  top  of  substances  that 
will  ferment  and  create  heat  underneath  the 
soil.  This  heat  from  beneath  will  force  vege- 
tation and  cause  a  much  larger  growth  than 


Coal.  25 

there  will  be  if  left  to  the  sun's  rays  alone. 
During  the  carboniferous  age  the  earth  was  a 
great  hotbed. 

The  fossils  of  trees  and  plants,  as  well  as 
reptiles,  that  we  find  in  the  great  coal  measures 
of  the  world,  show  that  they  were  of  large 
tropical  growth,  and  this  is  shown  not  only  in 
the  temperate  zone,  but  in  the  zone  farther 
north.  For  ages  and  ages  this  rank  growth  of 
vegetation  grew  up  and  fell  down  until  a  great 
layer  of  vegetable  matter  was  formed,  which  at 
a  later  time  was  covered  over  by  other  strati- 
fications of  earth  material,  so  that  these  great 
layers  of  vegetable  formation  were  hermeti- 
cally sealed  and  pressed  down  by  an  enormous 
weight  that  increased  as  time  went  on.  The 
formation  of  coal  may  be  studied  even  at  this 
day  (for  it  is  now  going  on)  by  visiting  and 
examining  the  great  peat  beds  that  are  found 
in  various  parts  of  the  world.  It  is  well 
known  that  peat  is  used  as  a  fuel  by  many 
people,  especially  the  peasantry  of  the  old 
countries.  If  peat  is  pressed  to  a  sufficient 
degree  of  hardness  it  burns  in  a  manner  not 
unlike  some  forms  of  coal.  Peat  is  a  vege- 
table formation  and  has  been  formed  by  the 
rank  growth  of  various  kinds  of  vegetation  in 
swampy  places.  Of  course,  it  lacks  the  purity 
of  the  coal  that  was  formed  during  the  car- 
boniferous age,  because  of  the  much  slower 
growth  of  vegetation  now  than  during  that 


26  future's  /nMracles. 

time,  and  the  opportunity  that  peat  bogs  offer 
for  an  intermixture  of  earthy  with  the  vege- 
table matter.  The  fact  that  we  find  the  im- 
print of  trees  and  ferns  and  other  vegetable 
growth  of  tropical  varieties,  as  well  as  the  fos- 
sils of  reptiles,  imbedded  in  the  coal  measures, 
proves  that  at  one  time  this  stratum  was  at 
the  land  surface  of  the  earth.  We  also  find 
that  all  of  the  formations  of  the  Secondary 
and  Tertiary  periods  are  on  top  of  the  coal — 
and  this  shows  that  after  the  age  of  rank 
vegetable  growth  there  was  a  sinking  of  the 
earth  in  many  places  far  down  into  the  ocean 
— so  that  vast  layers  of  rock  formed  on  top 
of  these  beds  of  vegetable  matter.  In  Eng- 
land great  chalk  beds  crop  out  in  cliffs  on  the 
southern  coast,  and,  as  we  have  seen,  these 
chalk  rocks  are  largely  made  up  of  the  shells 
of  marine  animals.  London  stands  on  a  chalk 
bed,  from  six  hundred  to  eight  hundred  feet 
thick.  Indeed,  England  has  been  poetically 
called  Albion,  White-land,  from  this  appear- 
ance of  her  coast. 

All  of  the  great  chalk  beds  were  formed 
ages  after  the  coal  beds,  as  the  latter  are 
found  in  the  upper  strata  of  the  Paleozoic 
period. 

A  study  of  these  strata  will  show  that  there 
are  many  layers  of  coal  strata  varying  in 
thickness  and  separated  by  layers  of  shale  and 
sandstone.  How  the  shale  and  sandstone 


CoaL  27 

layers  are  formed  will  be  the  subject  of  a 
future  chapter. 

From  the  position  that  the  coal  measures 
occupy,  being  entirely  under  the  Secondary 
and  Tertiary  formations,  it  will  be  observed 
that  they  are  very  old.  If  we  should  examine 
a  piece  of  ordinary  bituminous  coal  we  should 
find  that  there  are  lines  of  cleavage  in  it  paral- 
lel to  each  other,  and  that  it  is  an  easy 
matter  to  separate  the  lump  on  these  lines. 
If  we  examine  the  outcrop  of  a  coal  bed  we 
will  find  that  these  lines  of  cleavage  are  hori- 
zontal. This  indicates  that  the  great  bulk  of 
vegetable  matter  of  which  the  coal  formation 
is  made  up  has  been  subjected  to  tremendous 
pressure  during  a  long  period  of  time.  If  we 
further  examine  the  structure  of  a  body  of 
coal  we  find  the  impressions  of  limbs  and 
branches  as  well  as  the  leaves  of  trees  and 
various  kinds  of  plants.  We  shall  further 
find  that  these  impressions  lie  in  a  plant  in 
the  same  direction  as  the  line  of  cleavage. 
This  is  a  point  to  be  remembered,  as  it  helps 
to  explain  the  nature  and  structure  of  other 
formations  than  those  of  coal.  Not  only  are 
leaves  and  branches  of  vegetable  matter  found, 
but  fossils  of  reptiles,  such  as  live  on  the  land. 
Sometimes  there  is  found  the  fossil  of  a  great 
tree  trunk  standing  in  an  erect  position,  with 
its  roots  running  down  into  the  rock  below 
the  coal  bed,  while  the  trunk  extends  upward 


Iftature'e  /llMracles* 

entirely  through  the  coal  and  high  up  into  the 
other  strata.  All  of  these  facts  lead  us  to  the 
firm  conclusion  that  when  the  trees  were 
grown  that  formed  these  beds  they  were  above 
the  surface  of  the  ocean.  This,  taken  in  con- 
nection with  the  fact  that  the  vegetable  fos- 
sils that  are  found  indicate  a  tropical  growth 
of  great  size,  drives  us  to  the  conclusion  that 
the  climate  at  the  time  these  coal  measures 
were  formed  was  much  warmer  than  it  is  now. 
As  already  remarked,  this  extra  warmth 
came  from  the  earth  itself  before  it  had  cooled 
down  to  its  present  temperature,  rather  than 
from  the  heat  of  tl  e  sun.  There  is  nothing 
inconsistent  in  the  thought  that  the  sun  may 
have  been  warmer  in  a  former  age  than  now. 
We  may  conceive  that  the  earliest  coal  forma- 
tions took  place  when  the  land  stood  above  the 
surface  of  the  water,  and  that  the  conditions 
were  favorable  for  a  rapid  and  luxuriant 
growth  of  vegetation;  after  this  had  gone  on 
for  a  very  long  period  of  time,  by  some  con- 
vulsion of  nature  the  land  surface  was  sub- 
merged under  the  ocean,  when  other  mineral 
substances  were  deposited  on  top  of  this  layer 
of  vegetable  growth,  which  hardened  into  a 
rock  formation.  At  a  later  period  the  earth 
was  again  elevated  above  the  surface  of  the 
water  and  the  same  process  of  growth  and  de- 
cay was  repeated.  These  oscillations  of  the 
earth  up  and  down  occurred  at  enormously 


CoaU  29 

long  intervals,  until  all  of  the  various  coal 
strata  with  their  intermediate  formations 
were  completed.  After  this  we  must  suppose 
that  the  whole  was  submerged  to  a  great  depth 
and  for  a  very  long  period  of  time,  because  of 
the  great  number  and  various  kinds  of  rock 
formations  laid  down  by  water  that  lie  on  top 
of  the  coal  measures.  This  tremendous  weight, 
as  it  was  gradually  builded  up,  subjected  these 
vegetable  strata  to  an  inconceivable  pressure. 
In  some  places  this  pressure  was  much  greater 
than  in  others,  which  undoubtedly  is  one  of 
the  reasons  why  we  find  such  differences  in 
the  structure  and  quality  of  coal.  There  were 
no  doubt  many  other  reasons  for  differences, 
one  of  them  being  the  character  of  the  vege- 
table growth  out  of  which  they  were  formed. 
Again,  in  some  parts  of  the  world  these  coal 
-  strata  may  have  been  subjected  to  a  consider- 
able degree  of  heat,  which  would  change  the 
structure  of  the  formation,  and  in  some  cases 
drive  off  the  volatile  gases.  One  can  easily 
imagine  that  heat  was  thus  a  factor  in  the  for- 
mation of  what  is  known  as  anthracite  coal, 
so  much  less  gaseous  than  the  bituminous 
kinds.  The  anthracite  beds  seem  to  be  denser 
and  of  a  more  homogeneous  character.  The 
lines  of  cleavage  are  not  as  prominent,  but 
there  are  the  same  evidences  of  vegetable 
origin  that  we  find  in  the  bituminous  forma- 
tions. 


30  fftature'0  /BMracles. 

It  will  be  seen  from  what  has  gone  before 
that  coal  was  first  wood.  But  wood  is  a 
product  of  sunshine.  Thus  the  sun  was  the 
architect  and  builder  of  the  trees  and  plants 
that  were  finally  hermetically  sealed  under  the 
great  earth  strata.  The  sun  gathered  up  the 
material  and  set  the  forces  in  play  which  made 
the  chemical  combinations  of  the  various  ele- 
ments in  nature  that  enter  into  vegetable 
growth. 

After  the  lapse  of  untold  ages  of  time  these 
great  beds  of  stored-up  sun-energy  were  dis- 
covered by  man  and  their  contents  are  dragged 
out  to  the  earth's  surface,  to  warm  our  houses, 
to  drive  the  machinery  of  our  factories,  to 
send  the  locomotives  flying  across  the  conti- 
nents and  the  steamships  over  the  oceans.  So 
important  has  this  article  become  that  if  any 
one  nation  could  control  the  output  it  would 
be  able  to  paralyze  all  the  navies  and  the 
manufacturing  of  the  world. 

If  the  coal  of  the  world  should  become  ex- 
hausted we  should  be  confronted  with  a  great 
problem.  Fortunately  for  us,  this  is  a  prob- 
lem that  will  have  to  be  solved  by  the  people 
of  some  future  age,  as  the  growth  of  wood  will 
scarcely  keep  pace  with  the  consumption  of 
fuel.  By  that  time  the  genius  of  man  will 
have  devised  an  economical  means  of  storing 
the  energy  of  the  sunbeams  directly  for  pur- 
poses of  heat,  light,  and  power. 


CHAPTER  IV. 

SLATE  AND  SHALE. 

Slate  is  one  of  the  great  commercial 
products  of  the  world.  As  far  back  as  the 
year  1877  the  output  of  slate  was  not  less  than 
1,000,000  tons  per  annum.  The  chief  use  to 
which  slate  is  put  is  for  covering  buildings, 
and  for  this  purpose  it  is  better  than  any  other 
known  material.  It  is  also  used  in  the  con- 
struction of  billiard  tables  and  for  writing- 
slates;  these  latter  uses  are  very  insignificant 
as  compared  to  its  use  in  architecture.  Slate, 
like  building-stone  and  limestone,  is  quarried 
from  the  earth's  crust  and  is  found  in  the 
strata  close  above  the  Metamorphic  rocks,  near 
the  beginning  of  what  is  called  the  Primary, 
or  Paleozoic  period.  As  compared  with  the 
coal  formations  it  is  very,  very  old. 

There  are  different  substances  called  slate 
that  are  not  slate  in  the  scientific  use  of  that 
word.  In  general  all  stone  formations  are 
called  slates  that  split  up  into  thin  layers. 
But  the  true  slate  is  a  special  material  which 
is  formed  by  special  processes  of  nature.  The 

31 


32  fiature's 

difference  between  slate  and  shale,  for  in- 
stance, is  not  one  of  ingredients,  but  of  the 
process  by  which  the  ingredients  are  put  to- 
gether. All  of  the  sedimentary  rocks  are 
formed  by  a  deposit  of  sediment  from  the 
water  on  the  bottom  of  the  ocean.  At  one 
period  the  floods  have  brought  down  a  certain 
kind  of  material  in  greater  profusion  than  at 
others,  and  this  is  deposited  in  thin  layers, 
and  as  it  hardens  there  will  be  seams  in  it  and 
the  stratifications  will  be  differently  colored, 
the  color  depending  upon  the  deposit  at  any 
particular  time. 

A  bed  of  shale,  like  a  bed  of  coal,  has  lines 
of  cleavage  in  it,  and  if  it  is  examined  under 
a  microscope  it  will  be  found  that  the  sedi- 
mentary particles,  like  the  twigs  and  leaves  in 
the  coal  veins,  lie  with  their  longest  dimen- 
sions in  line  with  the  plane  of  cleavage. 
Shale  in  color  looks  like  slate,  and  an  analysis 
of  the  material  of  which  it  is  formed  shows 
that  shale  and  slate  are  both  made  from  the 
same.  There  is,  however,  a  structural  differ- 
ence between  the  two  which  is  very  peculiar 
and  very  interesting.  The  slate  is  ordinarily 
a  denser  material  and  the  lines  of  cleavage  are 
often  at  right  angles  with  those  that  we  find 
in  ordinary  shale. 

A  slab  of  shale  will  be  of  a  uniform  color  on 
any  one  line  of  cleavage.  The  color  may 
change  at  the  next  line,  and  generally  does,  to 


Slate  anD  Sbale.  33 

a  slight  extent.  It  is  easy  to  see,  then,  if  we 
could  change  the  lines  of  cleavage  in  the  shale, 
so  as  to  run  at  right  angles  with  their  present 
lines,  the  face  of  a  slab  would  show  bands 
of  different  colors  or  shadings,  such  as  we 
often  see  in  slate.  If  you  take  a  piece  of  clay 
that  has  been  thoroughly  mixed,  and  subject 
it  to  a  very  great  pressure,  and  then  examine 
the  piece  that  has  been  submitted  to  pressure 
under  a  microscope  and  compare  it  with  a 
piece  of  the  clay  after  it  has  been  thoroughly 
mixed,  but  has  not  been  submitted  to  pressure, 
you  will  find  that  the  two  are  very  different  in 
structure.  The  pressed  clay  will  show  that 
the  particles  of  which  it  is  made  up  have  all 
turned,  so  that  their  longest  dimensions  are  in 
a  line  at  right  angles  with  the  direction  of 
pressure.  Here  is  an  interesting  fact  that  we 
must  remember.  And  it  is  in  this  that  we 
find  the  reason  for  the  structural  difference 
between  shale  and  slate.  The  lines  of  cleav- 
age in  shale  are  not  formed  necessarily  by 
pressure,  but  because  in  the  disposition  of  the 
material  of  which  it  was  formed  the  particles 
naturally  laid  themselves  down  so  that  their 
longest  dimensions  were  on  a  horizontal  line. 
Ages  after,  when  other  rock  and  other  for- 
mations had  been  laid  down  on  top  of  the  bed 
of  deposited  mud,  the  upheavals  of  the  earth 
have  so  changed  the  lines  of  pressure  upon 
this  material  and  the  pressure  is  so  great  that 


34  Matured  /HMracles, 

a  re-arrangement  of  the  particles  of  which  the 
slate  is  made  up  has  taken  place,  so  that  their 
longest  dimensions  now  are  in  a  direction  that 
crosses  the  stratifications  as  originally  laid 
down. 

The  effect  of  this  is  twofold.  First,  the 
material  is  compressed  into  a  denser,  closer 
form,  and  then,  the  lines  of  cleavage  are 
changed,  or  to  express  it  in  more  common  lan- 
guage, the  grain  has  been  changed.  So  that 
when  it  splits  up  it  runs  crosswise  of  the 
original  layers  as  the  water  deposited  them, 
and  this  produces  the  different  shadings  so 
often  seen  in  different  slate.  Shale  splits  in 
line  with  its  layers;  slate  splits  across  that 
line. 

Let  us  go  back  a  moment  to  our  experiment 
with  the  lump  of  clay.  If  we  examined  the 
mixture  before  submitted  to  pressure  we 
should  find  that  the  oblong  particles  of  which 
it  was  made  up  would  stand  in  all  directions, 
hit  or  miss,  and  if  we  should  dry  this  lump  of 
clay  it  would  have  no  special  lines  of  cleavage. 
But  the  moment  we  have  submitted  it  to  a 
certain  amount  of  pressure  we  find  that  lines 
of  cleavage  have  been  established,  and  that  the 
particles  have  been  rearranged  so  that  their 
longest  dimensions  are  all  in  one  direction, 
which  coincides  with  the  cleavage  lines.  If 
we  should  now  take  this  same  piece  of  clay 
and  subject  it  to  a  pressure  at  right  angles  to 


Slate  anfc  Sbale*  35 

that  of  the  first  experiment  we  should  find  that 
the  lines  of  cleavage  had  also  changed  and  that 
the  particles  had  all  been  re-arranged.  Apply 
the  principle  to  the  formation  of  slate,  and  we 
can  understand  how  it  happens  that  what  we 
call  the  grain  runs  crosswise  of  the  deposits 
that  were  made  at  different  times.  It  is  not 
a  chemical,  but  purely  a  mechanical  difference. 
Or,  to  express  it  differently — the  difference  is 
a  structural  one  produced  by  mechanical 
causes. 

The  origin  of  cleavage  in  slate  has  been  the 
subject  of  much  speculation  and  investigation, 
but  like  many  other  problems  it  was  solved 
through  the  invention  and  application  of  the 
microscope.  Thin  layers  of  slate  have  been 
made,  the  same  as  with  limestone  and  chalk,  so 
thin  that  the  light  would  readily  pass  through 
it  and  that  an  examination  of  the  particles 
could  be  readily  made,  showing  their  arrange- 
ment under  varied  conditions.  Science  is  in- 
debted to  the  microscope  for  the  solution  of 
very  many  problems  that  for  ages  before  had 
puzzled  philosophers. 


CHAPTEK  V. 

SALT. 

It  may  seem  curious  to  the  reader  that  we 
should  care  to  discuss  a  subject  seemingly  so 
simple  as  common  salt.  But  it  is  a  very 
usual  thing  for  us  to  live  and  move  in  the 
presence  of  things  that  are  very  common  to 
our  everyday  experience,  and  yet  know 
scarcely  anything  about  them,  beyond  the  fact 
that  they  in  some  way  serve  our  purpose. 

Salt  is  one  of  the  commonest  articles  used 
In  the  preparation  of  our  food.  It  has  been 
questioned  by  some  people  whether  salt  was 
a  real  necessity  as  an  animal  food,  or  whether 
the  taste  for  it  is  merely  an  acquired  one.  All 
peoples  in  all  ages  seem  to  have  used  salt,  and 
reference  to  it  is  made  in  the  earliest  his- 
tories. Travelers  tell  us  that  savage  tribes, 
wherever  they  exist,  are  as  much  addicted  to 
the  use  of  salt  as  civilized  people.  One  of  the 
early  African  travelers,  Mungo  Park,  tells  us 
that  the  children  of  central  Africa  will  suck 
a  piece  of  rock  salt  with  the  same  avidity  and 


Salt.  31 

seeming  satisfaction  as  the  ordinary  civilized 
child  will  a  lump  of  sugar. 

All  animals  seem  to  require  salt,  and  it  is 
claimed  by  those  who  have  tried  the  experi- 
ment that  after  one  has  refrained  from  the 
use  of  salt  for  a  certain  length  of  time  the 
craving  for  it  becomes  exceedingly  painful. 
It  is  most  likely  that  the  taste  for  salt  is  a 
natural  craving.  In  any  event,  whether  it  is 
a  natural  or  an  artificial  taste,  it  has  become 
an  article  of  the  greatest  importance  in  the 
preparation  of  food,  as  well  as  on  account  of 
its  use  in  the  arts.  Salt  is  a  compound  of 
chlorine  and  sodium.  In  chemical  language 
it  is  called  sodium  chloride.  The  symbol  is 
NaCl,  which  means  that  a  molecule  of  salt  is 
composed  of  one  atom  of  sodium  and  one  of 
chlorine.  Chlorine  is  an  exceedingly  poison- 
ous gas. 

Formerly  the  chemist  when  he  wished  to 
obtain  sodium  extracted  it  from  common  salt 
and  discharged  the  chlorine  gas  into  the  air. 
It  was  found  that  in  establishments  where  the 
manufacture  of  sodium  was  conducted  on  a 
large  scale  the  destructive  properties  of  the 
chlorine  discharged  into  the  air  was  such  that 
all  vegetation  was  killed  for  some  distance 
around  the  manufactory.  This  came  to  be 
such  a  nuisance  that  the  manufacturers  were 
either  compelled  to  stop  business  or  in  some 
way  take  care  of  the  chlorine.  This  is  done 


38  Iftature'a  /BMracles. 

at  the  present  day  by  uniting  the  chlorine  gas 
with  common  lime,  forming  a  chloride  of  lime, 
which  is  used  for  bleaching  and  purifying 
purposes. 

Salt  is  found  in  great  quantities  as  a 
natural  product  under  the  name  of  rock  salt. 
It  is  found  in  some  parts  of  the  world  in  great 
veins  over  100  feet  in  thickness.  In  some 
cases  the  rock  salt  is  mined,  when  it  has  to  be 
purified  for  commercial  purposes.  The  com- 
mon mode  of  obtaining  salt,  however,  is  by 
pumping  the  solution  from  these  great  beds 
where  it  is  mingled  with  water — salt  water; 
the  water  is  then  evaporated,  and  when  it 
reaches  a  certain  stage  of  evaporation  the  salt 
crystallizes  and  falls  to  the  bottom. 

Different  substances  crystallize  in  different 
forms.  The  crystallization  of  water  when  it 
freezes,  as  we  shall  see  hereafter,  arranges 
its  molecules  in  such  a  form  as  to  make  a 
lump  of  ice  of  given  dimensions  lighter  than 
the  same  dimensions  of  water  would  be.  Salt 
in  crystallizing  does  not  follow  the  same  law; 
the  salt  crystal  is  in  the  shape  of  a  cube  and  is 
denser  in  its  crystalline  form  than  in  solution, 
hence  it  is  heavier  and  falls  to  the  bottom. 

It  is  said  that  there  is  a  deposit  of  rock  salt 
in  Galicia,  Austria,  covering  an  area  of 
10,000  square  miles.  There  are  also  very 
large  deposits  in  England,  the  mining  of 
which  has  become  a  great  industry.  There 


Salt  39 

are  also  great  beds  of  salt  in  various 
parts  of  the  United  States,  notably  near 
Syracuse,  1ST.  Y.,  where  large  salt  deposits 
were  exposed  in  an  old  river  bed  formed 
in  pre-glacial  times.  The  common  mode  of 
preparing  salt  for  domestic  purposes  is  by  the 
process  of  evaporation  from  brine  that  has 
been  pumped  from  salt  wells.  The  quality  of 
the  salt  is  determined  largely  by  the  tempera- 
ture at  the  time  of  evaporating  the  water  from 
it.  Ordinary  coarse  salt,  such  as  is  used  for 
preserving  meat  or  fish,  is  made  at  a  tempera- 
ture of  about  110  degrees;  what  is  known  as 
common  salt  is  made  at  a  temperature  of 
about  175  dgrees;  while  common  fine  or  table 
salt  is  made  at  a  temperature  of  220  degrees. 
Thus  it  will  be  seen  that  the  process  of  granu- 
lation with  reference  to  its  fineness  is  deter- 
mined by  the  rapidity  of  evaporation.  Salt  is 
one  of  the  principal  agents  in  preserving  all 
kinds  of  meats  against  putrefaction.  It  will 
also  preserve  wood  against  dry  rot.  Vessel 
builders  make  use  of  this  fact  to  preserve  the 
timbers  used  in  the  construction  of  the  vessels. 
Salt  at  the  present  day  is  very  cheap,  but  at 
the  beginning  of  the  present  century  it  was 
worth  from  $60  to  $70  per  ton.  The  methods 
of  decomposing  salt  to  obtain  its  constituents, 
which  are  used  in  various  other  compounds, 
are  very  simple  to-day  as  compared  with  the 
processes  that  prevailed  in  the  days  before  the 


40  flature's  /llMracles, 

advent  of  electricity  in  large  volume,  such  as 
is  produced  by  the  power  of  Niagara  Palls. 
It  is  curious  to  note  that  a  substance  so  useful 
and  so  harmless  as  common  salt  should  be 
made  out  of  two  such  refractory  and  danger- 
ous elements  as  chlorine  and  sodium.  Both 
of  these  elements,  standing  by  themselves, 
seem  to  be  out  of  harmony  with  nature,  but 
when  combined  there  are  few  substances  that 
serve  a  better  purpose. 

These  great  salt  beds  that  are  found  to  exist 
in  England  and  America  and  other  parts  of 
the  world  were  undoubtedly  deposited  from  the 
water  of  the  ocean  at  some  stage  in  the  forma- 
tion of  the  earth's  crust.  It  is  well  known 
that  sea  water  is  exceedingly  saline;  300  gal- 
lons of  sea  water  will  produce  a  bushel  of  salt. 
Undoubtedly  beds  of  salt  are  also  formed  by 
inland  lakes,  such  as  the  Great  Salt  Lake  in 
Utah.  Only  about  2.7  per  cent,  of  ocean  water 
is  salt,  while  the  water  of  the  Great  Salt  Lake 
of  Utah  contains  about  17  per  cent.  When 
there  is  so  much  salt  in  water  that  it  is  called 
a  saturated  solution,  salt  crystals  will  form 
and  drop  to  the  bottom,  which  process  will  in 
time  build  up  under  a  large  body  of  salt  water 
a  great  bed  of  rock  salt. 

The  water  in  all  rivers  and  springs  contains 
salt  to  a  certain  degree,  and  where  it  runs  into 
a  basin  like  that  of  a  lake  with  no  outlet, 
through  the  process  of  evaporation  pure  water 


Salt  41 

is  being  constantly  carried  off,  leaving  the  salt 
behind.  It  is  easy  to  see  that  if  this  process 
is  kept  up  long  enough  the  water  will  become 
in  time  a  saturated  solution,  when  crystalliza- 
tion sets  in  and  precipitation  follows,  account- 
ing for  the  deposits  of  rock  salt. 


AIR. 
CHAPTEE  VI. 

THE     ATMOSPHERE. 

Meteorology  is  a  science  that  at  one  time  in- 
cluded astronomy,  but  now  it  is  restricted  to 
the  weather,  seasons,  and  all  phenomena  that 
are  manifested  in  the  atmosphere  in  its  rela- 
tion to  heat,  electricity,  and  moisture,  as  well 
as  the  laws  that  govern  the  ever-varying  con- 
ditions of  the  circumambient  air  of  our  globe. 
The  air  is  made  up  chiefly  of  oxygen  and 
nitrogen,  in  the  proportions  of  about  twenty- 
one  parts  of  oxygen  and  seventy-nine  parts 
nitrogen  by  volume,  and  by  weight  about 
twenty-three  parts  oxygen  and  seventy-seven 
of  nitrogen.  These  gases  exist  in  the  air  as 
free  gases  and  not  chemically  combined.  The 
air  is  simply  a  mixture  of  these  two  gases. 

There  is  a  difference  between  a  mixture  and 
a  compound.  In  a  mixture  there  is  no  chem- 
ical change  in  the  molecules  of  the  substances 
mixed.  In  a  compound  there  has  been  a  re- 


Btmospbere,  43 

arrangement  of  the  atoms,  new  molecules  are 
formed,  and  a  new  substance  is  the  result. 

About  99  1-2  per  cent,  of  air  is  oxygen  and 
nitrogen  and  one-half  per  cent,  is  chiefly  car- 
bon dioxide.  Carbon  dioxide  is  a  product  of 
combustion,  decay,  and  animal  exhalation.  It 
is  poison  to  the  animal,  but  food  for  the  vege- 
table. However,  the  proportion  in  the  air  is 
so  small  that  its  baneful  influence  upon  ani- 
mal life  is  reduced  to  a  minimum.  The  nitro- 
gen is  an  inert,  odorless  gas,  and  its  use  in  the 
air  seems  to  be  to  dilute  it,  so  that  man  and 
animals  can  breathe  it.  If  all  the  nitrogen 
were  extracted  from  the  air  and  only  the  oxy- 
gen left  to  breathe,  all  animal  life  would  be 
stimulated  to  death  in  a  short  time.  The 
presence  of  the  nitrogen  prevents  too  much 
oxygen  from  being  taken  into  the  system  at 
once.  I  suppose  men  and  animals  might  have 
been  so  organized  that  they  could  breathe  pure 
oxygen  without  being  hurt,  but  they  were  not, 
for  some  reason,  made  that  way. 

Air  contains  more  or  less  moisture  in  the 
form  of  vapor;  this  subject,  however,  will  be 
discussed  more  fully  under  the  head  of  evapo- 
ration. The  air  at  sea-level  weighs  fifteen 
pounds  to  the  square  inch,  and  if  the  whole 
envelope  of  air  were  homogeneous — the  same 
in  character — it  would  reach  only  about  five 
miles  high.  But  as  it  becomes  gradually  rare- 
fied as  we  ascend,  it  probably  extends  in  a 


/iMracles. 

very  thin  state  to  a  height  of  eighty  or  ninety 
miles;  at  least,  at  that  height  we  should  find 
a  more  perfect  vacuum  than  can  be  produced 
by  artificial  means.  The  weight  of  all  the  air 
on  the  globe  would  be  11  2-3  trillion  pounds  if 
no  deduction  had  to  be  made  for  space  filled  by 
mountains  and  land  above  sea-level.  As  it  is, 
the  whole  bulk  weighs  something  less  than  the 
above  figures. 

As  we  have  said,  the  air  envelopes  the  globe 
to  a  height  at  sea-level  of  eighty  or  ninety 
miles,  gradually  thinning  out  into  the  ether 
that  fills  all  interstellar  space.  We  live  and 
move  on  the  bottom  of  a  great  ocean  of  air. 
The  birds  fly  in  it  just  as  the  fish  swim  in  the 
ocean  of  water.  Both  are  transparent  and 
both  have  weight.  Water  in  the  condensed 
state  is  heavier  than  the  air  and  will  seek  the 
lowest  places,  but  when  vaporized,  as  in  the 
process  of  evaporation,  it  is  lighter  than  air 
and  floats  upward.  In  the  vapor  state  it  is 
transparent  like  steam.  If  you  study  a  steam 
jet  you  will  notice  that  for  a  short  distance 
after  it  issues  from  the  boiler  it  is  transparent, 
but  soon  it  condenses  into  cloud. 

If  we  could  see  inside  of  a  boiler  in  which 
steam  had  been  generated,  all  the  space  not 
occupied  with  water  would  seem  to  be  vacant, 
since  steam  before  it  is  condensed  is  as  trans- 
parent as  the  air.  We  will,  however,  speak  of 
this  subject  more  fully  under  the  head  of 


Btmospbere*  45 

evaporation  and  cloud  formation.  It  is  not 
enough  that  we  have  the  air  in  which  we  live 
and  move,  with  all  of  its  properties,  as  we  have 
described :  something  more  is  needed  which  is 
absolutely  essential  both  to  animal  and  vege- 
table life — and  this  essential  is  motion.  If 
the  air  remained  perfectly  still  with  no  lateral 
movement  or  upward  and  downward  currents 
of  any  kind,  we  should  have  a  perfectly  con- 
stant condition  of  things  subjected  only  to 
such  gradual  changes  as  the  advancing  and  re- 
ceding seasons  would  produce  owing  to  the 
change  in  the  angle  of  the  sun's  rays.  No 
cloud  would  ever  form,  no  rain  would  ever 
fall,  and  no  wind  would  ever  blow.  It  is  of 
the  highest  importance  not  only  that  the  wind 
shall  blow,  but  that  comparatively  sudden 
changes  of  temperature  take  place  in  the  at- 
mosphere, in  order  that  vegetation  as  well  as 
animal  life  may  exist  upon  the  surface  of  the 
globe.  The  only  place  where  animal  life  could 
exist  would  be  in  the  great  bodies  of  water, 
and  it  is  even  doubtful  if  water  could  remain 
habitable  unless  there  were  means  provided 
for  constant  circulation — motion. 

The  mobility  of  the  atmosphere  is  such  that 
the  least  influence  that  changes  its  balance 
will  put  it  in  motion.  While  we  can  account 
in  a  general  way  for  atmospheric  movements, 
there  are  many  problems  relating  to  the  details 
that  are  unsolved.  We  find  that  even  the 


46  lftature'0 

"weather  man"  makes  mistakes  in  his  prog- 
nostications; so  true  is  this  that  it  is  never 
safe  to  plan  a  picnic  for  to-morrow  based  upon 
the  predictions  of  to-day.  The  chief  difficulty 
in  the  way  of  solving  the  great  problems  relat- 
ing to  the  sudden  changes  in  the  weather  and 
temperature  lies  in  the  fact  that  two-thirds  or 
more  of  the  earth's  surface  is  covered  with 
water;  thus  making  it  impossible  to  establish 
stations  for  observation  that  would  be  evenly 
distributed  all  over  the  earth's  surface. 
Enough  is  known,  however,  to  make  the  study 
of  meteorology  a  most  wonderfully  interesting 
subject. 

We  have  already  stated  that  air  is  com- 
posed of  a  mixture  of  oxygen  and  k&fe&gen. 
chiefly,  with  a  small  amount  of  carbon  dioxide. 
So  far  as  the  life  and  health  of  the  animal  is 
concerned  we  could  get  along  without  this 
latter  substance,  but  it  seems  to  be  a  necessity 
in  the  growth  of  vegetation.  There  are  other 
things  in  the  air  which,  while  they  are  unneces- 
sary for  breathing  purposes,  it  will  be  well  for 
us  to  understand,  as  some  of  them  are  things 
to  be  avoided  rather  than  inhaled. 

As  before  mentioned,  air  contains  moisture, 
which  is  a  very  variable  quantity.  In  a  cold 
day  in  winter  it  is  not  more  than  one-thou- 
sandth part,  while  in  a  warm  day  in  summer 
it  may  equal  one-fortieth  of  the  quantity  of 
air  in  a  given  space.  There  is  also  a  small 


ttbe  Btmospbere.  47 

amount  of  ammonia,  perhaps  not  over  one- 
sixty-millionth.  Oxygen  also  exists  in  the 
air  in  very  small  quantities  in  another  form 
called  ozone.  One  way  to  produce  ozone 
is  by  passing  an  electric  spark  through  air. 
Anyone  who  has  operated  a  Holtz  machine  has 
noticed  a  peculiar  smell  attending  the  disrup- 
tive discharges,  which  is  the  odor  of  ozone.  It 
is  what  chemists  call  an  allotropic  form  of 
oxygen,  just  as  the  diamond,  graphite,  and 
charcoal  are  all  different  forms  of  carbon,  and 
yet  the  chemical  differences  are  scarcely  trace- 
able. It  is  more  stimulating  to  breathe  than 
oxygen  and  is  probably  produced  by  lightning 
discharges. 

As  has  been  before  stated,  the  oxygen  of  the 
air  is  consumed  by  all  processes  of  combustion, 
and  in  this  we  include  the  breathing  of  men 
and  animals  and  the  decay  of  vegetable  mat-, 
ter,  as  well  as  the  more  active  combustion  aris- 
ing from  fires.  A  grown  person  consumes 
something  over  400  gallons  of  oxygen  per  day, 
and  it  is  estimated  that  all  the  fires  on  the 
earth  consume  in  a  century  as  much  oxygen 
as  is  contained  in  the  air  over  an  area  of 
seventy  miles  square.  All  of  these  processes 
are  throwing  into  the  air  carbon  dioxide  (car- 
bonic acid),  which,  however,  is  offset  by  the 
power  of  vegetation  to  absorb  it,  where  the 
carbon  is  retained  and  forms  a  part  of  the 
woody  fiber  and  pure  oxygen  is  given  back  into 


48  matured 

the  air.  By  this  process  the  normal  condi- 
tions of  the  air  are  maintained. 

One  decimeter  (nearly  4  inches)  square  of 
green  leaves  will  decompose  in  one  hour  seven 
cubic  centimeters  of  carbon  dioxide,  if  the 
sun  is  shining  on  them;  in  the  shade  the  same 
area  will  absorb  about  three  in  the  same  time. 

There  is  another  substance  in  the  form  of 
vegetable  germs  in  the  air  called  bacteria.  At 
one  time  these  were  supposed  to  be  low  forms 
of  animal  life,  but  it  is  now  determined  that 
they  are  the  lowest  forms  of  vegetable  germs. 
Bacteria  is  the  general  or  generic  name  for  a 
large  class  of  germs,  many  of  them  disease 
germs.  By  analysis  of  the  air  in  different  lo- 
cations and  in  different  parts  of  the  country 
it  has  been  determined  that  on  the  ocean  and 
on  the  mountain  tops  these  germs  average 
only  one  to  each  cubic  yard  of  air.  In  the 
streets  of  the  average  city  there  are  3000  of 
them  to  the  cubic  yard,  while  in  other  places 
where  there  is  sickness,  as  in  a  hospital  ward, 
there  may  be  as  many  as  80,000  to  the  cubic 
yard.  These  facts  go  to  prove  what  has  long 
been  well  known,  that  the  air  of  a  city  fur- 
nishes many  more  fruitful  sources  for  disease 
than  that  of  the  country.  Some  forms  of  bac- 
terial germs  are  not  considered  harmful,  and 
they  probably  perform  even  a  useful  service  in 
the  economy  of  nature.  Within  certain  limits, 
other  things  being  equal,  the  higher  one's 


Btmospbere,  49 

dwelling  is  located  above  the  common  level  the 
purer  will  be  the  air.  This  rule,  however,  has 
its  limits,  as  the  oxygen  of  the  air  is  heavier 
than  the  nitrogen,  so  that  the  air  at  very  great 
altitudes  has  not  the  same  proportion  of  oxy- 
gen to  nitrogen  that  it  has  at  a  lower  level. 
An  analysis  that  was  made  some  years  ago  of 
the  air  on  the  west  shore  of  Lake  Michigan, 
especially  that  section  where  the  bluffs  are 
high,  shows  that  it  compares  favorably  with 
that  of  any  other  portion  of  the  United 
States. 

In  view  of  the  foregoing,  it  is  of  the  highest 
importance  to  the  sanitary  condition  of  any 
city,  town,  or  village  that  it  be  not  too  com- 
pactly built.  If  more  than  a  certain  number 
of  people  occupy  a  given  area,  it  is  absolutely 
impossible  to  preserve  perfect  sanitary  condi- 
tions. And  there  ought  to  be  a  State  law, 
especially  for  all  suburban  towns,  which  are 
the  homes  and  sleeping  places  for  large  num- 
bers of  business  men  who  spend  their  days  in 
the  foul  air  of  the  city,  stipulating,  that  the 
houses  shall  be  not  less  than  a  certain  distance 
apart.  Oxygen  is  the  great  purifier  of  the 
blood,  and  if  one  does  not  get  enough  of  it  he 
suffers  even  though  he  breathes  no  impurities. 
The  power  to  resist  the  effects  of  bad  air  is 
much  greater  when  one  is  awake  and  active 
than  when  asleep,  and  this  is  why  it  is  more 
important  to  sleep  in  pure  air  than  to  be  in  it 


50  nature's  Miracles. 

during  our  waking  hours.  It  is  best,  however, 
to  be  in  good  air  all  of  the  time.  By  pure  air 
I  do  not  mean  pure  oxygen,  but  the  right  mix- 
ture of  the  two  gases  that  make  air.  Too 
much  of  a  good  thing  is  often  worse  than  not 
enough.  Pure  food  to  eat,  pure  water  to 
drink,  and  pure  air  to  breathe  would  soon  be 
the  financial  ruin  of  a  large  class  of  doctors. 


CHAPTEE  VII. 

AIR  TEMPERATURE. 

The  most  recent  definition  of  heat  is  that 
it  is  a  mode  of  motion;  not  movement  of  a 
mass  of  substance,  but  movement  of  its  ulti- 
mate particles.  It  has  been  determined  by 
experiment  that  the  ability  of  any  substance 
to  absorb  heat  depends  upon  the  number  of 
atoms  it  contains,  rather  than  its  bulk  or  its 
weight. 

It  has  also  been  stated  that  the  atmosphere 
at  sea-level  weighs  about  fifteen  pounds  to  the 
square  inch,  which  means  that  a  column  of 
air  one  inch  square  extending  from  sea-level 
upward  to  the  extreme  limit  of  the  atmosphere 
weighs  fifteen  pounds.  The  density  of  the  air 
decreases  as  we  ascend.  Each  successive 
layer,  as  we  ascend,  is  more  and  more  ex- 
panded, and  consequently  has  a  less  and  less 
number  of  air  molecules  in  a  given  space. 
Therefore  the  capacity  of  the  air  for  holding 
heat  decreases  as  we  go  higher. 

We  deduce  from  these  facts  that  the  higher 
we  go  the  colder  it  becomes;  and  this  we  find 
to  be  the  case.  Whoever  has  ascended  a  high 

51 


52  flature'0 

mountain  has  had  no  difficulty  in  determin- 
ing two  things.  One  is  that  the  air  is  very 
much  colder  than  at  sea-level,  and  the  other 
that  it  is  very  much  lighter  in  weight.  We 
find  it  difficult,  when  we  first  reach  the  sum- 
mit, to  take  enough  of  oxygen  into  our  lungs 
to  carry  on  the  natural  operations  of  the 
bodily  functions.  To  overcome  this  difficulty, 
if  we  remain  at  this  altitude  for  a  considerable 
time,  we  shall  find  that  our  lungs  have  ex- 
panded, so  as  to  make  up  in  quantity  what  is 
lacking  in  quality. 

If  a  man  lives  for  a  long  time  at  an  altitude 
of  10,000  feet  he  will  find  that  his  lungs  are 
so  expanded  that  he  experiences  some  difficulty 
when  he  comes  down  to  sea-level.  And  the 
reverse  is  true  with  one  whose  lungs  are 
adapted  to  the  conditions  we  find  at  sea-level, 
when  he  ascends  to  a  higher  altitude.  There 
is  a  constant  endeavor  on  the  part  of  nature  to 
adapt  both  animal  and  vegetable  life  to  the 
surroundings.  While  no  exact  formula  has 
been  established  as  to  the  rate  of  decrement  of 
temperature  as  we  ascend,  we  may  say  that  it 
decreases  about  one  degree  in  every  300  or  400 
feet  of  ascent.  There  is  no  exact  way  of  ar- 
riving at  this,  as  in  ascending  a  mountain  the 
temperature  will  be  more  or  less  affected  by 
local  conditions.  If  we  go  up  in  a  balloon  we 
have  to  depend  upon  the  barometer  as  a  means 
of  measuring  altitude,  which,  owing  to  the 


Bfr  {Temperature.  53 

varying  atmospheric  conditions,  is  not  a  reli- 
able mode  of  measurement.  It  is  easily  under- 
stood that  a  cubic  foot  of  air  at  sea-level  will 
contain  a  great  many  more  atoms  than  a  cubic 
foot  of  air  will  at  the  top  of  a  high  mountain ; 
or,  to  state  it  in  another  way,  a  cubic  foot  of 
air  at  sea-level  will  occupy  much  more  than  a 
cubic  foot  of  space  10,000  feet  higher  up. 
Suppose,  then,  that  the  amount  of  heat  held 
in  a  cubic  foot  of  air  at  sea-level  remained  the 
same,  as  related  to  the  number  of  atoms.  In 
its  ascent  we  shall  find  that  at  a  high  altitude 
the  same  number  of  atoms  that  were  held  at 
sea-level  in  a  cubic  foot  have  been  distributed 
over  a  so  much  larger  space  that  the  sensible 
heat  is  greatly  diminished  or  diluted,  so  to 
speak.  It  was  an  old  notion  that  heat  would 
hide  itself  away  in  fluids  under  a  name  called 
by  scientists  latent  heat.  This  theory  has 
been  exploded,  however,  by  modern  investiga- 
tion. 

If  we  place  some  substance  that  will  inflame 
at  a  low  temperature  in  the  bottom  of  what  is 
called  a  fire  syringe  (which  is  nothing  but  a 
cylinder  bored  out  smoothly,  with  a  piston 
head  nicely  fitted  to  it,  so  that  it  will  be  air- 
tight) and  then  suddenly  condense  the  air  in 
the  syringe  by  shoving  the  plunger  to  the  bot- 
tom, we  can  inflame  the  substance  which  has 
been  placed  in  the  bottom  of  the  cylinder.  In 
this  operation  the  heat  that  was  distributed 


54  flaturc'0 

through  the  whole  body  of  air,  that  was  con- 
tained in  the  cylinder  before  it  was  com- 
pressed, is  now  condensed  into  a  small  space. 
If  we  withdraw  the  plunger  immediately,  be- 
fore the  heat  has  been  taken  up  by  the  walls  of 
the  syringe,  we  shall  find  the  air  of  the 
same  temperature  as  before  the  plunger  was 
thrust  down.  This,  however,  does  not  take 
into  account  any  heat  that  was  generated  by 
friction. 

Let  us  further  illustrate  the  phenomenon  by 
another  experiment.  If  we  suddenly  compress 
a  cubic  foot  of  air  at  ordinary  pressure  into  a 
cubic  inch  of  space,  that  cubic  inch  will  be 
very  hot  because  it  contains  all  the  heat  that 
was  distributed  through  the  entire  cubic  foot 
before  the  compression  took  place.  Now  let 
it  remain  compressed  until  the  heat  has  radi- 
ated from  it,  as  it  soon  will,  and  the  air  be- 
comes of  the  same  temperature  as  the  sur- 
rounding air.  What  ought  to  happen  if  then 
we  should  suddenly  allow  this  cubic  inch  of 
air  to  expand  to  its  normal  pressure,  when  it 
will  occupy  a  cubic  foot  of  space? 

Inasmuch  as  we  allowed  the  heat  to  escape 
from  it  when  in  the  condensed  form,  when  it 
expands  it  will  be  very  cold,  because  the  heat 
of  the  cubic  inch,  now  reduced  to  the  normal 
temperature  of  the  surrounding  air,  is  dis- 
tributed over  a  cubic  foot  of  space. 

This  is   precisely  what  takes  place  when 


Bit  temperature.  55 

heated  air  at  the  surface  of  the  earth  (which 
is  condensed  to  a  certain  extent)  rises  to  the 
higher  regions  of  the  atmosphere.  There  is  a 
gradual  expansion  as  it  ascends,  and  conse- 
quently a  gradual  cooling,  because  a  given 
amount  of  heat  is  being  constantly  distributed 
over  a  greater  amount  of  space.  At  an  alti- 
tude of  forty-five  miles  it  will  have  expanded 
about  25,000  times,  which  will  bring  the  tem- 
perature down  to  between  200  and  300  degrees 
below  zero. 

When  we  get  beyond  the  limits  of  the  at- 
mosphere we  get  into  the  region  of  absolute 
cold,  because  heat  is  atomic  motion,  and  there 
can  be  no  atomic  motion  where  there  are  no 
atoms. 

We  have  now  traced  the  atmosphere  up  to 
the  point  where  it  shades  off  into  the  ether 
that  is  supposed  to  fill  all  interplanetary  space. 
As  Dryden  says : 

There  fields  of  light  and  liquid  ether  flow, 
Purg'd  from  the  pond'rous  dregs  of  earth  below. 

By  interplanetary  space  we  mean  all  space 
between  the  planets  not  occupied  by  sensible 
material.  It  is  the  same  as  interatomic  space, 
or  the  space  between  atoms,  except  in  degree, 
as  the  same  substance  that  fills  interplanetary 
space  also  fills  interatomic  space,  so  that  all 
the  atoms  of  matter  float  in  it  and  are  held 
together  from  flying  off  into  space  by  the  at- 


56  IRature's  /UMraclee* 

traction  of  cohesion.  What  this  ether  is,  has 
been  the  subject  of  much  speculation  among 
philosophers,  without,  however,  arriving  at 
any  definite  conclusion,  further  than  that  it  is 
a  substance  possessing  almost  infinite  elas- 
ticity, and  whose  ultimate  particles,  if  par- 
ticles there  be,  are  so  small  that  no  sensible 
substance  can  be  made  sufficiently  dense  to  re- 
sist it  or  confine  it.  It  is  easy  to  see  that  a 
substance  possessing  such  qualities  cannot  be 
weighed  or  in  any  way  made  appreciable  to 
our  senses.  But  from  the  fact  that  radiant 
energy  can  be  transmitted  through  it,  with 
vibrations  amounting  to  billions  per  second, 
we  know  that  it  must  be  a  substance  with 
elastic  qualities  that  approach  the  infinite. 
Assuming  that  the  ether  is  a  substance,  the 
question  arises  how  is  it  related  to  other  forms 
of  substance?  This  is  a  question  more  easily 
asked  than  answered.  The  longer  one  dwells 
upon  the  subject,  however,  the  more  one  is 
impressed  with  the  thought  that  after  all  the 
ether  may  be  the  one  element  out  of  which  all 
other  elements  come. 

Chemistry  tells  us  that  there  are  between 
sixty  and  seventy  ultimate  elements.  This  is 
true  at  least  as  a  basis  for  chemical  science. 
Chemical  analysis  has  never  been  able  to  make 
gold  anything  but  gold,  or  oxygen  anything 
but  oxygen,  and  so  on  through  the  whole  cata- 
logue of  elements.  It  may  be,  however,  that 


Bit  {Temperature*  57 

the  play  of  forces  under  and  beyond  those  that 
seem  to  be  active  in  all  chemical  processes  and 
relations,  are  able  to  produce  certain  affections 
of  the  ether,  the  result  of  which  in  the  one 
case  is  an  atom  of  gold  and  in  the  other  an 
atom  of  oxygen,  etc.,  to  the  end  of  the  list.  In 
this  case  all  of  the  so-called  elements  may  have 
their  origin  in  one  fundamental  element  that 
we  call  the  ether.  I  am  aware  that  we  are 
wading  in  deep  water  here,  but  sometimes  we 
love  to  get  into  deep  water  just  to  try  our 
swimming  powers.  The  above  is  a  suggestion 
of  a  theory  called  "  the  vortex  theory,"  that  is 
taking  root  in  the  minds  of  many  philosophers 
to-day,  and  yet  there  is  almost  nothing  of 
known  facts  to  base  such  a  theory  upon,  and 
nearly  all  we  can  say  about  it  is  that  it  seems 
plausible,  when  viewed  through  the  eye  of 
imagination. 

We  do  know  that  substances,  such  as  fluids 
or  gases,  assume  very  different  qualities  when 
put  into  different  rates  of  motion.  A  straw 
has  been  known  to  penetrate  the  body  of  a 
tree  endwise  by  the  extreme  velocity  imparted 
to  it  when  carried  in  the  vortex  of  a  tornado. 
Instances  of  the  terrific  solid  power  of  sub- 
stances that  are  mobile  when  at  rest  are  often 
exhibited  during  the  progress  of  a  tornado, 
especially  when  confined  in  very  narrow  limits. 
Sometimes  a  tornado  cloud  will  form  a  hang- 
ing cone,  running  down  to  a  sharp  point  at  the 


58  matured  /HMraclcs, 

lower  end,  whict  lower  end  may  drag  on  the 
ground,  or  it  may  float  a  little  distance  above 
the  ground,  but  more  frequently  it  moves  for- 
ward with  a  bounding  motion,  now  touching 
the  earth  and  now  rising  in  the  air.  This 
cone  is  revolving  at  a  terrific  speed.  The  sub- 
stance revolving  is  chiefly  air,  carrying  other 
light  substances  that  it  has  gathered  up  from 
the  ground.  If  it  comes  in  contact  with  a 
tree  or  building  it  cuts  its  way  through  as 
though  it  were  a  buzzsaw  revolving  at  a  high 
rate  of  speed.  This  is  not  simply  the  force  of 
wind,  but  a  kind  of  solidity  given  to  the  fluent 
air  by  its  whirling  motion. 

I  remember  a  case  in  Iowa,  where  one  of 
these  revolving  cones  passed  through  a  barn- 
yard, striking  the  corner  of  the  barn,  cutting 
it  off  as  smoothly  as  though  done  with  some 
sharp-edged  tool,  but  it  in  no  other  way  af- 
fected the  rest  of  the  building.  One  would 
suppose  that  the  centrifugal  force  developed 
in  this  whirling  motion  would  cause  the  cone 
to  fly  apart,  and  why  it  does  not  no  one  cer- 
tainly knows.  But  we  are  obliged  to  accept 
the  fact. 

These  cases  are  cited  to  show  that  motion 
gives  rigidity  to  substances  that  in  the  quies- 
cent state  are  mobile  or  easily  moved,  like  the 
straw  or  the  air.  If  we  should  assume  that 
there  are  infinitesimal  vortices  or  whirling 
rings  in  the  ether,  of  such  rapidity  as  to  give 


2llr  {Temperature*  59 

it  different  degrees  of  rigidity,  we  can  get  a 
glimmering  idea  of  how  an  atom  of  matter 
may  be  formed  from  ether. 

Eef erring  to  the  rigidity  which  motion  gives 
to  ordinary  matter,  it  is  well  known  that  when 
two  vessels  at  sea  collide  the  one  having  the 
higher  speed  is  not  so  liable  to  injury  as  the 
one  with  the  lower.  The  reader  will  perhaps 
remember  a  circumstance  said  to  have  oc- 
curred a  few  years  ago  on  the  Lake  Shore 
Railroad,  between  Buffalo  and  Cleveland. 
The  limited  express  was  going  west,  and  while 
rounding  a  curve  the  engineer  suddenly  came 
in  sight  of  a  wrecked  freight  train,  a  part  of 
which  was  lying  on  the  track  where  the  express 
train  had  to  pass.  The  engineer  saw  that  he 
was  too  near  the  wreck  to  stop  his  train  and 
that  the  only  way  to  save  his  own  train  and 
the  lives  of  his  passengers  would  be  to  cut 
through  the  wreck.  He  pulled  out  the  throttle 
and  put  on  a  full  head  of  steam,  and  when  the 
train  struck  the  wreck  it  was  going  at  such  a 
high  rate  of  speed  that  it  cut  through  without 
seriously  damaging  the  train  and  without 
harm  to  the  passengers. 

There  are  other  heroes  beside  those  who  lead 
armies  in  battle. 


CHAPTEE  VIII. 

CLOUD-FORMATION — EVAPORATION. 

Water  exists  in  different  forms  without, 
however,  undergoing  any  chemical  change.  It 
is  when  condensed  into  the  fluid  state  that  we 
call  it  "water,"  and  then  it  is  heavier  than 
the  atmospheric  air  and  therefore  seeks  the 
low  places  upon  the  earth's  surface,  the  lowest 
of  which  is  the  bed  of  the  ocean.  Wherever 
there  is  water  or  moisture  on  the  face  of  the 
globe  there  is  a  process  going  on  at  the  surface 
called  evaporation.  This  process  is  much 
more  rapid  under  the  action  of  heat  than  when 
it  is  colder.  In  other  words,  as  the  heat  in- 
creases evaporation  increases  within  certain 
limits  and  bears  some  sort  of  a  ratio  to  it. 
Evaporation  is  not  confined  to  water,  but  as 
our  subject  has  to  deal  with  atmospheric  phe- 
nomena we  will  speak  of  it  only  in  its  rela- 
tion to  aqueous  moisture. 

The  heat  that  is  imparted  to  the  earth's 
surface  by  the  rays  of  the  sun  is  able  to  sepa- 
rate water  into  minute  particles,  which,  when 
so  separated,  form  what  is  called  vapor,  which 

60 


Clout>*3formaticm— jSvaporation.       61 

is  transparent,  as  well  as  much  lighter  than 
the  air  at  the  surface  of  the  earth.  Being 
lighter  than  the  air,  it  rises  when  disengaged 
and  floats  to  the  upper  regions  of  the  atmos- 
phere. The  atmosphere  will  contain  a  certain 
amount  of  these  transparent  globules  of  mois- 
ture in  the  spaces  between  its  own  molecules. 
If  the  air  is  warm  the  molecules  will  be 
farther  apart  and  it  will  contain  more  moist- 
ure than  when  it  is  cold. 

The  process  of  evaporation  is  one  of  the 
most  important  in  the  catalogue  of  nature's 
dynamics.  Without  it  there  would  be  no 
verdure  on  the  hills,  no  trees  on  the  plains,  no 
fields  of  waving  grain,  and  no  animal  life  upon 
the  land  surface  of  the  globe.  Evaporation  is 
nature's  method  of  irrigation,  and  the  system 
is  inaugurated  on  a  grand  scale,  so  that  there 
are  but  few  neglected  spots  upon  the  face  of 
the  earth  which  moisture,  carried  up  from  the 
great  reservoirs  of  water,  does  not  reach.  The 
rate  of  evaporation,  other  things  being  equal, 
depends  upon  the  extent  of  surface;  therefore 
a  smooth  surface  like  that  of  the  lake  or  ocean 
will  not  send  up  as  much  vapor  from  a  given 
area  in  square  miles  as  an  equal  area  of  land 
will  do,  when  it  is  saturated  with  moisture,  for 
the  reason  that  there  is  a  much  larger  evapor- 
ating surface  on  a  square  mile  of  land,  owing 
to  its  inequalities,  than  upon  an  equal  area  of 
smooth  water.  Of  course,  if  the  earth  is  dry 


62  'ftature'a  /HMracles. 

there  can  be  but  little  evaporation.  One  of 
the  effects  of  evaporation  is  to  withdraw  heat, 
and  so  to  produce  cold  in  the  substance  from 
which  the  evaporation  takes  place. 

If  we  put  water  into  a  vial  and  drop  regu- 
larly upon  it  some  fluid  that  evaporates  readily 
it  will  extract  the  heat  from  the  vial  and  the 
water  in  it  to  such  an  extent  that  in  a  short 
time  the  water  will  be  frozen.  In  hot  coun- 
tries ice  is  manufactured  on  a  large  scale  upon 
the  principle  that  we  have  just  described. 
Water  is  put  into  shallow  basins,  excavated  in 
the  earth,  over  which  is  placed  some  substance 
like  straw  that  readily  radiates  heat,  and  on 
the  straw  are  placed  porous  bricks,  that  are 
kept  wet,  thus  furnishing  a  very  large  evapor- 
ating surface.  In  this  way  the  process  of 
evaporation  is  carried  on  very  rapidly  and 
the  heat  is  extracted  from  the  water  to  such  an 
extent  that  it  freezes,  often  forming  ice  in  one 
night  over  an  inch  in  thickness,  and  this  in 
the  hottest  climates  on  the  globe.  Evapora- 
tion cannot  go  on  in  places  where  the  air  is  al- 
ready saturated  with  moisture.  When  the  air 
is  dry  evaporation  is  very  rapid,  but  as  it  be- 
comes more  and  more  filled  with  moisture  the 
evaporation  is  checked  to  the  same  degree. 
This  fact  accounts  for  the  difference  of  bodily 
comfort  that  we  experience  at  different  times 
in  the  year  when  the  temperature  is  the  same. 
Sometimes  we  are  very  uncomfortable  al- 


Clou&*fformation— Evaporation.       63 

though  the  temperature  is  not  above  75  de- 
grees Fahrenheit,  more  so  even  than  we  are  at 
other  times  when  the  temperature  is  ten  or 
fifteen  degrees  higher.  If  the  air  is  saturated 
with  moisture,  even  though  the  temperature  is 
not  above  70  or  75  degrees,  the  perspiration  is 
not  readily  evaporated  from  the  surface  of  the 
body.  If  the  air  is  dry  the  temperature  may 
be  much  higher  and  we  be  much  more  com- 
fortable, because  evaporation  goes  on  rapidly, 
which  keeps  the  body  not  only  dry,  but  cool. 
I  remember  passing  through  a  desert  in  Ari- 
zona where  there  was  scarcely  a  green  thing  in 
sight  in  any  direction,  and  the  temperature 
was  said  to  be  140  degrees.  I  did  not  suffer 
as  much  as  I  often  have  done  in  the  East  with 
the  thermometer  at  80  or  90  degrees,  and 
there  was  very  little  show  of  sensible  perspira- 
tion ;  it  was  going  on  rapidly,  however,  but  was 
being  absorbed  by  the  dry  air.  This  goes  to 
show  that  temperature  is  not  the  only  factor 
to  be  considered  when  we  are  making  an  esti- 
mate of  the  good  or  bad  qualities  of  a  climate. 
Evaporation  is  carried  on  much  more 
rapidly  when  the  wind  blows  than  at  other 
times,  for  the  reason  that  the  moisture  is 
carried  off  laterally  as  fast  as  it  is  formed, 
all  resistance  to  its  escape  into  the  upper  air 
being  removed.  If  the  air  is  charged  to  satu- 
ration with  moisture  at  a  certain  temperature, 
it  will  remain  so,  and  evaporation  stops  so 


64  future's 

long  as  the  temperature  remains  unchanged. 
If  its  temperature  rises  the  process  of  evapo- 
ration can  start  up,  because  the  capacity  of  the 
air  for  holding  moisture  has  been  increased. 
But  if  a  temperature  is  perceptibly  lowered 
another  phenomenon  will  manifest  itself. 

In  the  uncondensed  state  vaporized  moisture 
is  quite  transparent,  so  that  we  are  able  to 
see  through  it  as  we  do  through  a  pane  of 
glass.  If,  however,  the  body  of  air  that  is 
saturated  with  this  invisible  moisture  becomes 
suddenly  chilled,  the  moisture  condenses  into 
cloud  or  mist. 

If  we  watch  a  passing  railroad  train  we  shall 
notice  a  mass  of  fleecy  white  mist  floating 
away  from  the  smokestack,  assuming  the  bil- 
lowy forms  of  some  of  the  clouds  in  summer. 
This  cloud  is  produced  by  the  sudden  conden- 
sation of  steam,  which  was  transparent  before 
it  came  in  contact  with  the  cold,  outside  air, 
the  effect  being  much  more  pronounced  in  cold 
than  in  warm  weather.  We  may  liken  these 
floating  globules  of  mist  to  the  dust  of  the 
earth  which  floats  in  the  air,  and  it  has  not 
been  inaptly  called  water-dust.  Anyone  who 
has  seen  an  atomizer  used  or  has  stood  at  the 
foot  of  a  great  waterfall,  like  Niagara,  has 
seen  the  fluid  so  finely  divided  that  it  will  float 
in  the  air,  instead  of  falling  to  the  ground. 
What  takes  place  is  that  a  number  of  these 
transparent  atoms  of  moisture  that  are  re- 


ClouD^fformation— ^Evaporation.       65 

leased  in  the  process  of  evaporation  coalesce 
into  one  small  drop  or  particle  of  water,  and 
they  will  continue  to  float  in  the  air  as  mist 
or  cloud  until  a  sufficient  number  have  com- 
bined into  one  solid  mass  to  render  that  mass 
heavier  than  the  air,  when  it  falls  in  the  form 
of  rain. 

If  we  live  in  a  region — and  there  are  such 
on  the  face  of  the  earth — where  there  is  very 
little  evaporation  and  consequently  very  little 
moisture  in  the  air,  there  is  rarely  ever  a  cloud 
seen  nor  is  there  any  rainfall,  for  the  reason 
that  there  is  no  material  existing  out  of  which 
to  form  clouds,  and  the  clouds  precede  the 
rain.  Hence,  all  the  artificial  attempts  to  pro- 
duce rain  in  these  arid  regions  have  been 
futile.  If  a  body  of  warm  air,  when  saturated 
with  invisible  moisture,  is  suddenly  chilled  by 
coming  in  contact  with  a  cold  wave,  it  is 
squeezed  like  a  sponge,  so  to  speak,  and  the 
invisible  particles  become  visible  because  a 
number  of  them  have  coalesced  as  one  par- 
ticle ;  the  particles  gather  in  a  large  mass,  and 
we  have  the  phenomenon  of  cloud  formation. 

Clouds  more  generally  form  in  the  upper 
regions  of  the  atmosphere  because  it  is  nor- 
mally colder  in  the  higher  regions.  In  some 
cases  clouds  float  very  high  in  the  air  and  in 
others  very  low.  This  is  due  to  two  causes: 

If  we  should  send  up  a  balloon  containing 
air  rarefied  to  a  certain  extent  it  would  con- 


66  Iftature's  /IIMraclee, 

tinue  to  ascend  only  until  it  reached  a  point 
where  the  outside  air  and  that  contained  in 
the  balloon  are  of  the  same  density.  If  we 
should  send  up  this  same  balloon  on  different 
days  with  the  same  rarefaction  of  internal  air 
we  should  find  that  on  some  days  it  would  float 
higher  than  others,  because  the  density  of  the 
air  is  constantly  fluctuating,  as  is  indicated 
by  the  rise  and  fall  of  the  barometer.  Now 
let  us  consider  the  balloon  as  a  globule  of 
moisture  of  a  definite  weight,  and  this  globule 
only  one  of  an  aggregation  of  globules  suffi- 
cient to  form  a  cloud.  We  can  readily  see 
from  what  has  gone  before  that  a  cloud  thus 
formed,  having  a  definite  density  and  weight, 
would  float  higher  some  days  than  others. 

Assuming  again  that  the  density  of  the  air 
remains  the  same  from  day  to  day,  the  clouds 
will  still  float  high  or  low  in  the  atmosphere 
from  another  cause.  Let  us  go  back  to  our 
illustration  of  the  balloon.  If  we  have  a  fixed 
condition  of  atmosphere,  external  to  the  bal- 
loon,'and  vary  the  conditions  internally,  which 
means  varying  its  weight,  the  balloon  will 
float  higher  or  lower  as  the  internal  conditions 
are  varied.  Now  apply  this  principle  to  the 
moisture  globules  of  which  a  cloud  is  formed 
and  we  can  understand  why  a  cloud*  will  float 
high  or  low  from  the  two  causes  that  we  have 
described.  Clouds  are  of  different  color  and 
density,  and  this  is  due  to  the  differences  of 


— ^Evaporation,       67 

the  make-up  of  the  moisture  globules  of  which 
the  clouds  are  formed.  If  these  globules  are 
in  an  advanced  stage  of  condensation  the 
cloud  is  darker  and  more  opaque.  In  earlier 
conditions  of  condensation  the  cloud  will  have 
a  bright  look,  which  shows  that  it  reflects  most 
of  the  light,  whereas  in  the  case  of  the  dark 
cloud  the  light  is  largely  absorbed. 

There  is  a  sort  of  notion  prevailing  that 
clouds  come  up  from  the  horizon,  and  in  many 
cases  they  do,  but  they  may  form  directly  over 
our  heads.  There  always  has  to  be  a  begin- 
ning, and  that  occurs  wherever  the  conditions 
are  most  favorable  for  condensation  of  vapor. 
If  the  earth  is  wet  and  the  sun  is  hot  the 
evaporation  may  be  very  rapid  as  well  as  the 
ascent  of  the  invisible  moisture,  which  carries 
with  it  the  air,  which  in  turn  expands  the 
higher  it  rises,  thus  producing  cold.  This, 
taken  with  the  normal  cold  that  exists  in  the 
higher  regions,  may  be  sufficient  to  produce  a 
sudden  condensation  of  this  ascending  vapor, 
which  is  all  that  is  necessary  to  form  a  cloud. 

The  inquiry  may  arise,  Why  is  the  moisture 
condensed,  almost  always,  in  the  upper  regions 
of  the  air,  where  it  is  rare  ?  Because  the  more 
rare  and  therefore  expanded  it  is,  the  more 
moisture  it  will  hold.  This,  taken  with  the 
fact  that  cold  currents  are  encountered  high 
up,  sufficiently  answers  the  question. 

It  is  interesting  to  know  that  the  processes 


68  matured  flMracles, 

of  nature  are  interdependent.  It  is  not 
enough  that  we  have  the  evaporation  of  mois- 
ture that  will  ascend  into  the  higher  regions  of 
the  air  and  there  be  condensed  into  cloud  and 
possibly  rain,  but  we  must  have  the  means  for 
distributing  these  conditions  over  a  large  area, 
and  for  this  purpose  we  have  the  phenomenon 
of  wind.  Why  the  winds  blow  can  be  ac- 
counted for  to  a  certain  extent, — we  might  say 
to  a  large  extent, — but  there  yet  remain  many 
unsolved  problems  relating  to  wind  and 
weather.  Of  the  phenomena  of  wind  we  will 
speak  more  fully  in  a  future  chapter. 


CHAPTEE  IX. 

CLOUD  FOKMATION — CONTINUED. 

As  water  in  its  condensed  state  is  815  times 
heavier  than  air,  the  question  naturally  comes 
to  one  why  it  does  not  immediately  fall  to  the 
earth  when  it  condenses.  There  are  at  least  two 
and  probably  more  stages  of  condensation.  In- 
vestigators into  the  phenomenon  of  cloud  for- 
mation claim  to  have  ascertained  that  the  first 
effect  of  condensation  is  to  form  little  globes 
of  moisture  that  are  hollow,  like  a  bubble,  with 
very  thin  walls.  Everyone  has  recognized  the 
ease  with  which  a  soap  bubble  will  float  in  the 
air,  and  yet  it  is  simply  a  film  of  moisture. 
These  little  balloons,  so  to  speak,  are  called 
spherules.  It  is  undoubtedly  the  case  that 
mingled  with  these  little  bubbles  of  moisture 
there  are  fine  particles  of  solid  water  hanging 
on  and  carried  along  with  them.  Undoubt- 
edly this  is  true;  at  least  just  before  the  final 
act  of  condensation  takes  place ;  and  when  the 
little  hollow  spherules  collapse  they  are  gath- 
ered together  in  drops  of  water  larger  or 
smaller  according  to  the  rapidity  of  condensa- 

69 


fo  matured  Miracles. 

tion.  There  is  probably  another  power  at 
work  to  prevent  the  too  ready  precipitation  of 
moisture  when  condensed,  and  that  is  the 
wind.  A  cloud  never  stands  still,  although  in 
some  cases  it  may  appear  to  do  so.  If  we  take 
a  stone  in  our  hand  and  allow  it  to  drop  with- 
out applying  any  force  to  it,  it  will  fall  di- 
rectly to  the  ground.  But  if  we  give  it  an  im- 
petus in  a  horizontal  direction  it  will  travel 
some  distance  before  striking  the  ground.  If 
we  could  give  the  same  impetus  to  a  body  as 
light  as  a  globule  of  water-dust  it  would  prob- 
ably travel  indefinitely  without  falling.  Dust 
that  would  settle  directly  to  the  ground  from 
an  elevation  in  still  air  would  travel  thousands 
of  miles  without  falling,  before  a  wind  having 
any  considerable  velocity. 

Suppose  the  sun  to  be  shining  with  intense 
heat  upon  a  certain  area  of  the  earth's  surface 
and  the  conditions  to  be  right  for  very  rapid 
evaporation  of  moisture.  The  air  which  is 
heated  close  to  the  ground,  being  expanded, 
will  rise,  together  with  the  invisible  particles 
of  moisture,  and  there  will  be  a  column  of 
moisture-laden  air  continually  ascending  until 
it  reaches  a  point  in  the  upper  atmosphere 
where  it  is  condensed  into  a  cloud  that  takes 
on  the  billowy  form  which  in  summer  time  we 
call  a  thunder  cloud,  but  which  in  the  science 
of  meteorology  is  called  cumulus,  or  heap- 
cloud.  If  there  were  no  air  currents  this  bil- 


ClouD  ^Formation*  ?i 

lowy  cloud  would  stand  as  the  capping  of  an 
invisible  pillar  of  ascending  vapor,  but  as  it  is 
never  the  case  that  air  is  not  moving  at  some 
velocity  in  the  upper  regions,  it  floats  away  as 
rapidly  as  it  is  formed.  This  peculiar  kind  of 
cloud  is  formed  in  the  mid-regions  of  the  at- 
mosphere, and  it  is  a  summer  cloud  as  well  as 
a  land  cloud.  Of  course,  it  may  float  off  over 
the  ocean  and  maintain  its  peculiar  shape  for 
a  certain  distance,  but  it  is  rare  that  such  a 
cloud  would  ever  be  seen  in  mid-ocean  or  in 
midwinter.  As  the  warm  season  advances  in 
summer,  and  evaporation  from  the  earth  is 
less  than  the  rainfall,  there  is  less  and  less 
moisture  in  the  air,  when,  of  course,  the  con- 
ditions for  cloud  formation,  especially  inland, 
are  not  so  favorable  as  in  the  early  spring  or 
summer.  Frequently  there  comes  a  time 
when  we  have  a  long  season  of  dry,  settled 
weather.  Probably  during  most  of  the  days 
clouds  will  form  and  we  think  it  is  going  to 
rain,  but  before  night  they  have  vanished,  and 
the  same  thing  is  repeated  the  next  day  and 
the  next,  perhaps  for  weeks  at  a  time. 

The  explanation  is  this:  We  have  already 
said  that  so  long  as  the  air  remains  in  a  uni- 
form condition  as  to  temperature  it  will  ab- 
sorb moisture  in  a  transparent  state  until  it 
is  filled  to  the  measure  of  its  capacity  at  a 
given  temperature.  If  there  were  no  change  of 
temperature,  it  would  not  condense  into  cloud. 


f  2  future's 

Clouds  may  be  absorbed  into  the  atmosphere 
— or  evaporated — and  become  invisible;  and 
this  process  is  going  on  to  a  greater  or  less  de- 
gree continually.  If  we  watch  the  steam  as  it 
escapes  from  a  steam  boiler,  the  first  effect  is 
condensation  into  cloud,  but  as  it  floats  away 
it  gradually  melts  and  is  absorbed  into  the  at- 
mosphere as  invisible  vapor.  This  is  espe- 
cially true  on  a  warm  day;  the  same  process 
takes  place  in  the  air  that  is  going  on  at  the 
level  of  a  body  of  water  or  at  the  surface  of 
moist  earth. 

As  before  stated,  condensation  always  takes 
place  when  a  body  of  moisture-laden  air  comes 
in  contact  with  cold.  When  the  steam  escapes 
from  a  boiler,  even  on  the  hottest  day,  it  is 
hotter  than  the  surrounding  air;  the  first 
effect  is  condensation,  and  then  evaporation 
takes  place  the  same  as  it  would  at  the  surface 
of  the  earth  when  the  condensed  particles  of 
moisture  are  separated  into  the  invisible  atoms 
that  accompany  evaporation. 

In  settled,  dry  weather  as  the  sun  ap- 
proaches the  zenith,  the  earth  becomes  in- 
tensely heated,  and  there  is  an  ascending 
column  of  air  partly  laden  with  moisture;  but 
not  to  the  same  extent  as  earlier  in  the  season. 
Condensation  takes  place  and  clouds  are 
formed,  but  as  there  is  not  sufficient  moisture 
to  carry  them  to  the  point  of  a  further  conden- 
sation,— which  would  result  in  precipitation, — 


Cloufc  formation.  V3 

as  the  sun  lowers  in  the  west  and  the  heated 
air  becomes  more  evenly  distributed  this  con- 
densed vapor  is  re-absorbed  into  the  air  as  in- 
visible moisture  by  a  process  allied  to  that  of 
evaporation.  This  condition  of  things  would 
extend  to  a  much  longer  period  than  it  does  in 
our  latitude  if  it  were  not  for  the  gradual 
changing  of  the  seasons,  which  finally  destroys 
the  balance  in  the  dynamics  of  cloud-land  and 
allows  the  cold — that  has  been  held  back  for 
the  time — in  the  great  northern  zone  to  get 
the  upper  hand.  Then  we  have  what  is  termed 
in  common  parlance  a  change  in  the  weather, 
or,  more  properly  in  this  case,  a  change  in  the 
season. 

We  have  already  spoken  of  the  cloud  called 
cumulus  (which  means  heap)  and  of  its  per- 
formance during  the  dry  season  of  summer. 
There  is  another  form  of  cloud  that  is  seen  at 
this  season  of  the  year  called  cirrus  (a  curl). 
It  takes  the  form  of  a  curl  at  its  ends.  This 
cloud  usually  has  a  threaded  shape  and  some- 
times takes  the  form  of  a  feather,  and  fre- 
quently forms  are  seen  that  remind  you  of 
frost  pictures  on  a  window  pane.  These 
clouds  float  very  high  in  the  atmosphere, 
away  above  the  tops  of  the  highest  moun- 
tains, from  six  to  eight  miles  above  the 
level  of  the  sea.  They  are  formed  only  at  a 
season  of  the  year  when  the  atmospheric  con- 
ditions are  most  uniform.  At  certain  times 


V4  feature's  ASfracles. 

of  the  day  and  night  the  moisture  will  rise  to 
this  height  before  it  condenses  and  when  it 
does  condense  it  immediately  freezes,  which 
makes  it  take  on  these  peculiar  forms  that 
would  no  doubt  conform  very  closely  to  the 
frost  pictures  on  the  window  pane  if  it  were 
not  for  the  disturbing  influences  of  air  cur- 
rents at  this  altitude.  The  fact  that  they  are 
ice  or  frost  clouds  instead  of  water  clouds 
gives  them  that  peculiar  whiteness  and  bright- 
ness of  appearance.  If  ordinary  clouds  are 
water-dust  these  high  clouds  may  be  called  ice- 
dust.  Sometimes  we  see  them  lying  in  bands 
or  threads  running  across  the  sky  in  the  di- 
rection that  the  wind  blows.  Their  form  is 
undoubtedly  a  resultant  of  the  struggle  be- 
tween the  air  currents  and  the  tendency  of 
crystallized  water  to  arrange  itself  in  certain 
definite  lines  or  forms.  This  cloud  may  be 
said  to  be  one  extreme,  having  its  home  in 
the  highest  regions  of  cloud-land,  while  the 
cumulus,  or  thunder  cloud,  is  the  other  ex- 
treme and  occupies  the  lower  or  mid  regions 
of  the  air. 

There  is  a  still  lower  cloud  of  course,  as 
ordinary  fog  is  nothing  more  than  cloud, 
which  under  certain  conditions  lies  on  the 
surface  of  the  ocean  or  dry  land.  Fogs  pre- 
vail when  the  barometer  is  low.  As  soon  as 
it  rises  from  the  source  of  evaporation  the 
moisture  condenses  almost  to  the  point  of  pre- 


Cloud  formation.  ^5 

cipitation.  There  is  not  enough  buoyancy  in 
its  globules  when  the  air  is  light,  as  it  is  when 
we  have  a  low  barometer,  to  cause  the  fog  to 
float  into  the  higher  regions  of  the  atmosphere. 
The  high  clouds,  which  are  called  cirrus, 
under  certain  conditions  drop  down  to  where 
they  begin  to  melt  into  ordinary  moisture 
globules,  and  while  this  process  is  going  on  we 
have  a  combined  cloud  effect  which  is  called 
cirro-stratus.  This  form  of  cloud  may  be 
recognized,  when  looking  off  toward  the  hori- 
zon, by  its  being  formed  into  long  straight 
bands.  It  is  sometimes  called  thread-cloud. 
As  it  further  descends  it  takes  on  a  different 
form  called  the  cirro-cumulus,  or  curl-heap. 
This  is  just  the  opposite  in  its  appearance  to 
the  cirro-stratus,  as  it  is  broken  up  into  flocks 
of  little  clouds  separated  from  each  other  and 
in  the  act  of  changing  to  the  form  of  the 
cumulus,  or  billowy  form  of  cloud;  and  this 
latter  jbakes  place  when  it  drops  to  a  still  lower 
stratum  of  warmer  air  and  is  there  called  the 
cumulo-stratus,  which  is  the  form  of  cloud  we 
most  often  see  in  the  season  of  thunderstorms. 
The  lower  edge  of  the  cloud  is  straight,  par- 
allel with  the  horizon,  while  the  upper  part  is 
made  up  of  great  billowy  masses,  having  high 
lights  upon  their  well  defined  projections  and 
blending  into  darker  shades  caused  by  the 
shadows  in  the  valleys  between  the  mountains 
of  cloud. 


?6  matured  Afracle*. 

The  rain  cloud  is  called  the  nimbus,  and 
may  be  said  to  be  the  extension  of  a  cumulo- 
stratus.  When  it  reaches  this  condition  it  is 
condensed  to  a  point  where  the  vesicular 
globules  collapse  and  a  number  of  them  run 
together,  forming  a  solid  drop  of  water,  and 
here  it  begins  to  fall.  It  may  be  very  small  at 
first,  but  in  its  fall  other  condensed  globules 
will  adhere  to  it  and  if  the  conditions  are 
right,  sometimes  the  rain  drops  will  have  the 
diameter  of  a  quarter  of  an  inch  by  the  time 
they  reach  the  earth. 

IJnder  other  conditions,  such  as  we  have 
sometimes  during  dry  weather,  the  rain  drops 
will  start  to  fall,  but  instead  of  growing 
larger,  they  grow  smaller  by  absorption  into 
the  thirsty  air,  and  will  not  be  allowed  to  reach 
the  earth.  Often  there  are  showers  of  rain  in 
the  air  that  fall  to  a  certain  distance  and  are 
taken  up,  as  in  the  process  of  evaporation,  to 
again  be  formed  into  cloud,  without  ever  hav- 
ing touched  the  earth. 

Thus  it  will  be  seen  that  clouds  assume 
various  forms  under  various  conditions  of  at- 
mosphere, as  it  is  related  to  moisture,  tempera- 
ture, and  density.  Clouds  sometimes  appear 
to  be  stationary  when  they  are  only  continu- 
ally forming  on  one  side  and  continually 
being  absorbed  into  invisible  moisture  on  the 
other.  I  remember  seeing  some  wonderfully 
beautiful  cloud  effects  in  the  regions  of 


ClouD  formation,  W 

the  Alps.  Almost  every  day  in  summer  there 
appears  above  the  peak  of  Mount  Blanc  a 
beautifully  formed  cloud  cap  standing  some 
distance  above  it  and  hollowed  out  under- 
neath like  an  inverted  cup.  Although  this 
cloud  appears  to  be  stationary,  it  is  under- 
going a  rapid  change;  the  moisture  rises  from 
the  snow-capped  peak  as  invisible  vapor  to  a 
certain  distance,  where  it  is  condensed  into  a 
cloud  of  wonderful  brilliancy.  As  the  cloud 
globules  float  upward  they  are  absorbed  into 
the  atmosphere  again,  as  invisible  moisture  at 
the  upper  limit  of  the  cloud.  If  the  wind 
happens  to  be  blowing,  another  phenomenon 
takes  place,  giving  the  appearance  somewhat 
of  a  volcano.  It  is  blown  off  from  the  peak 
in  the  direction  of  the  wind,  but  within  a 
short  distance  it  strikes  a  warmer  stratum  of 
air,  where  it  is  absorbed  and  assumes  the 
transparent  condition. 

If  we  ascend  a  high  mountain,  we  get  some 
idea  of  the  altitude  of  the  various  forms  of 
cloud.  A  thunderstorm  may  be  in  progress 
far  below  us,  while  the  sun  may  be  shining 
from  a  clear  sky  above,  with  perhaps  the  ex- 
ception of  the  frost  clouds  that  we  have  re- 
ferred to  floating  high  above  the  mountain 
tops. 

We  have  now  described  in  a  general  way 
how  clouds  are  formed,  how  they  are  con- 
densed into  rain,  and  how  moisture  is  dis- 


'8  flature'6  /BMracles. 

tributed  over  large  areas  by  these  rain  clouds 
being  borne  on  the  wings  of  the  wind;  and 
now  you  ask,  Whence  the  wind?  In  our  next 
and  following  chapters  we  will  try  to  answer 
this  question. 


CHAPTER  X. 

WIND — WHY  IT  BLOWS. 

We  have  said  that  globules  of  moisture,  re- 
leased by  the  action  of  the  sun's  rays  in  the 
process  of  evaporation,  tend  to  rise  because 
they  are  lighter  than  the  air.  Right  here  let  it 
be  said  that  all  material  substances  have 
weight;  even  hydrogen,  the  lightest  known 
gas,  has  weight,  and  is  attracted  by  gravita- 
tion. If  there  were  no  air  or  other  gaseous 
substances  on  the  face  of  the  earth  except  hy- 
drogen, it  would  be  attracted  to  and  envelop 
the  earth  the  same  as  the  air  now  does.  Car- 
bon dioxide  is  a  gas  that  is  heavier  than  the 
air.  If  we  take  a  vessel  filled  with  this  gas 
and  pour  it  into  another  vessel  it  will  sink  to 
the  bottom  and  displace  the  air  contained  in 
it  until  the  air  is  all  driven  out.  If  we  fill  a 
jar  with  water  up  to  a  certain  height  and  then 
pour  a  pint  of  shot  into  it  the  water  will  be 
caused  to  rise  in  the  vessel  because  it  has  been 
displaced  at  the  bottom  by  the  heavier  ma- 
terial. RTow  if  we  remove  the  shot  the  water 

79 


So  Nature's 

will  recede  to  the  level  maintained  before  the 
shot  was  put  in.  On  the  contrary,  if  we 
should  pour  an  equal  bulk  of  cork  or  pith  balls 
into  the  jar  the  water  would  not  be  displaced, 
because  the  balls  are  lighter  than  the  water 
and  would  lie  on  top  of  it;  if,  however,  the 
water  is  removed  from  the  jar,  the  cork  will 
immediately  go  to  the  bottom  of  the  jar,  be- 
cause the  cork  is  heavier  than  the  air  which 
has  taken  the  place  of  the  water.  We  wish  to 
impress  upon  the  mind  of  the  reader  the  fact, 
that  all  substances  of  a  fluidic  nature,  whether 
in  the  fluid  or  gaseous  state,  have  weight,  and 
obey  the  laws  of  gravitation,  and  the  heavier 
portions  will  always  seek  the  lower  levels,  and 
in  doing  this  will  displace  the  lighter  por- 
tions, causing  them  to  rise.  There  is  no  ten- 
dency in  any  substance  to  rise  of  itself,  but 
the  lighter  substance  rises  because  it  is  forced 
to  do  so  by  the  heavier,  which  displaces  it. 
This  law  lies  at  the  bottom  of  all  of  the  phe- 
nomena of  air  currents. 

If  we  are  at  certain  points  on  the  seashore 
in  the  summer  time  we  may  notice  that  about 
9  o'clock  in  the  morning  a  breeze  will  spring 
up  from  the  ocean  and  blow  toward  the  land; 
this  will  increase  in  intensity  until  about  2 
o'clock  in  the  afternoon,  when  it  has  reached 
its  maximum  velocity,  and  from  this  time  it 
gradually  diminishes,  until  in  the  evening 
there  will  be  a  season  of  calm,  the  same  as 


1ft  ffilows*  81 

there  was  in  the  early  morning.  The  expla- 
nation of  this  peculiar  action  of  the  air  is 
found  in  the  fact  that  during  the  day  the  land 
is  heated  much  more  rapidly  on  its  surface 
than  the  water  is. 

The  radiant  energy  from  the  sun  is  sud- 
denly arrested  at  the  surface  of  the  earth, 
which  is  heated  to  only  a  very  shallow  depth, 
while  in  the  water  it  is  different ;  being  trans- 
parent it  is  penetrated  by  the  radiant  energy 
to  a  much  greater  depth  and  does  not  suddenly 
arrest  it,  as  is  the  case  on  land.  As  the  sun 
rises  and  the  rays  strike  in  a  more  and  more 
vertical  direction  the  earth  becomes  rapidly 
and  intensely  heated  at  its  surface,  and  this  in 
turn  heats  the  stratum  of  air  next  above  it, 
which  is  pressing  on  it  with  a  force  of  fifteen 
pounds  to  the  square  inch  at  sea-level.  When 
air  is  heated  it  expands,  and  as  it  expands  it 
grows  lighter.  The  stratum  lying  upon  the 
earth  as  soon  as  it  becomes  heated  moves  up- 
ward and  its  place  is  occupied  by  the  heavier, 
cooler  air  that  flows  in  from  the  sides.  We 
can  now  see  that  if  there  is  a  strong  ascending 
current  of  air  on  the  land  near  the  ocean  the 
cooler  air  from  the  surface  of  the  ocean  will 
flow  in  to  take  the  place  of  the  warmer  and 
lighter  air  that  is  driven  upward,  really  by 
the  force  of  gravity  which  causes  the  heavier 
fluid  to  keep  the  lowest  level.  As  the  earth 
grows  hotter  this  movement  is  more  and  more 


$2  Wature'0  Airacle*. 

rapid,  which  causes  the  flow  of  colder  air  to  be 
quickened,  and  hence  the  increasing  force  of 
the  wind  as  the  sun  mounts  higher  in  the 
heavens.  Eut  when  it  has  passed  the  point  of 
maximum  heating  intensity  and  the  earth  be- 
gins to  cool  by  radiation,  the  movements  of  air 
currents  begin  to  slow  up,  until  along  in  the 
evening  a  point  is  reached  where  the  surface 
of  the  earth  and  that  of  the  ocean  are  of  equal 
temperature,  and  there  is  no  longer  any  cause 
for  change  of  position  in  the  air. 

The  earth  heats  up  quickly,  and  it  also  cools 
quickly,  especially  if  there  is  green  grass  and 
vegetation.  While  they  are  poor  conductors 
of  heat,  they  are  excellent  radiators,  so  that 
when  the  sun's  rays  are  no  longer  active  the 
earth  cools  down  rapidly  and  soon  passes  the 
point  where  there  is  an  equilibrium  between 
the  land  and  water.  The  water  possesses  the 
opposite  quality.  It  is  slow  to  become  heated, 
because  of  a  much  larger  mass  that  is  affected, 
and  is  equally  slow  to  give  up  the  heat.  And 
the  consequence  is  that  after  the  sun  has  set, 
the  land  cools  so  much  faster  than  the  water 
that  we  soon  have  the  opposite  condition,  and 
the  sea  is  warmer  than  the  land,  which  makefc 
the  air  at  that  point  lighter,  and  which  in 
turn  causes  the  denser  or  colder  air  from  the 
land  to  flow  toward  the  ocean,  and  displace 
the  lighter  air  and  force  it  upward;  hence  we 
have  a  land  instead  of  a  sea  breeze.  So  that 


1Tt  Mom  83 


the  normal  condition  in  summer  is  that  of  a 
breeze  from  the  ocean  toward  the  land  during 
part  of  the  day  and  a  corresponding  breeze 
from  the  land  to  the  ocean  during  part  of 
the  night,  with  a  period  of  no  wind  during 
the  morning  and  evening  of  each  day. 

The  forces  that  work  to  produce  all  the 
varying  phenomena  of  air  currents  on  differ- 
ent portions  of  the  earth  are  difficult  to  ex- 
plain, as  there  are  so  many  local  conditions  of 
heat  and  cold,  and  these  are  modified  by  the 
advancing  and  receding  seasons.  The  un- 
equal distribution  of  land  and  water  upon  the 
earth's  surface  ;  the  readiness  with  which  some  . 
portions  absorb  and  radiate  heat  as  compared 
with  others;  the  tall  ranges  of  mountains, 
many  of  them  snow-capped;  the  lowlands  ad- 
jacent to  them  that  become  intensely  heated 
under  the  sun's  rays;  the  diversity  of  coast- 
line and  the  fact  that  there  is  a  zone  of  con- 
tinually heated  earth  and  water  in  the  tropical 
regions  —  all  these  conditions,  coupled  with  the 
fact  that  the  earth  rotates  on  its  axis  once  in 
twenty-four  hours,  are  certainly  sufficient  to 
account  for  all  the  complicated  phenomena  of 
aerial  changes  on  the  various  portions  of  the 
earth's  surface. 

The  trade  winds  are  so  called  because  they 
blow  in  a  certain  definite  direction  during  cer- 
tain seasons  of  the  year,  and  can  be  reckoned 
upon  for  the  use  of  commerce.  If  you  trace 


84  IRature'0 

the  line  of  the  equator  you  will  notice  that  for 
more  than  three-quarters  of  the  distance  it 
passes  through  the  water.  The  water,  as  we 
have  explained  in  the  last  chapter,  becomes 
gradually  heated  to  a  considerable  depth,  and 
when  once  saturated  with  heat  is  slow  to  give 
it  up.  It  can  easily  be  seen  that  there  will  be 
a  zone  extending  each  way  from  the  equator 
for  a  certain  distance  that  will  become  more 
intensely  heated  than  any  other  parts  of  the 
earth,  with  the  exception  of  certain  circum- 
scribed portions  of  the  land.  The  result  is 
that  this  heated  equatorial  zone  is  constantly 
sending  up  warm  air  caused  by  the  inrush  of 
colder  air,  which  is  heavier  than  the  air  at  the 
equator,  expanded  by  the  heat.  The  warm  air 
at  the  equator  is  forced  up  into  the  higher 
regions  of  the  atmosphere,  and  here  it  over- 
flows each  way,  north  and  south,  causing  a 
current  of  air  in  the  upper  regions  counter  to 
that  of  the  lower.  As  it  travels  north  and 
south  it  gradually  drops  as  it  becomes  cooler, 
and  finally  at  some  point  north  and  south  its 
course  is  changed  and  it  flows  in  again  toward 
the  equator.  As  a  matter  of  fact,  the  trade 
winds  do  not  flow  apparently  from  the  north 
and  south  directly  toward  the  equator,  but  in 
an  oblique  direction.  On  the  north  side  of  the 
equator  we  have  a  northeasterly  wind,  and  a 
southeasterly  wind  on  the  south  side.  This  is 
caused  by  the  rotation  of  the  earth  from  west 


1Ft  J5SIOW0.  B5 

to  east.  The  direction  of  the  trade  wind,  how- 
ever, is  more  apparent  than  real. 

The  earth  in  its  diurnal  revolutions  travels 
at  the  rate  of  a  little  more  than  1000  miles  an 
hour  at  the  equator.  But  if  we  should  travel 
northward  to  within  four  miles,  say,  of  the 
north  pole,  the  surface  point  would  be  mov- 
ing at  the  rate  of  only  about  a  mile  an  hour. 
At  some  point  equidistant  between  the  north 
pole  and  the  equator  the  surface  of  the  earth 
will  be  moving  at  a  rate,  say,  of  500  miles  an 
hour.  If  we  could  fire  a  projectile  from  this 
point  that  would  have  a  carrying  power  to  take 
it  to  the  equator  some  time  after  the  projectile 
was  fired,  although  it  would  fly  in  a  perfectly 
direct  line,  it  would  appear  to  anyone  at  the 
equator  who  observed  its  approach  to  be  mov- 
ing from  a  northeasterly  direction.  The  rea- 
son is  that  the  earth  is  traveling  twice  as  fast 
,  at  the  equator  as  it  is  at  the  point  whence  the 
projectile  is  fired.  Therefore  it  will  overshoot, 
so  to  speak,  at  the  equator,  and  not  be  dragged 
around  by  the  increased  motion  we  find  there. 

To  make  this  still  plainer,  suppose  the  earth 
to  be  standing  still  and  a  projectile  be  fired 
directly  across  from  the  north  pole  in  the  di- 
rection of  the  lines  of  longitude  and  required 
one  hour  to  reach  the  equator,  the  projectile 
would  appear  to  anyone  standing  at  the 
equator  to  come  directly  from  the  north.  If, 
however,  the  earth  is  revolving  at  the  rate  of 


86  flature'0  /ilMraclea, 

1000  miles  an  hour  at  the  equator  to  the  east- 
ward, and  the  projectile  was  fired  from  the 
pole,  where  there  is  practically  no  motion,  in 
the  same  direction  along  the  longitudinal  lines 
as  before,  the  observer  would  have  to  be  in  a 
position  on  the  equator  1000  miles  west  of 
this  longitudinal  line  in  order  to  see  the 
projectile  when  it  arrived;  therefore  the  ap- 
parent movement  of  the  projectile  would  not 
be  along  the  line  at  the  instant  that  it  was 
fired,  but  along  a  line  that  would  cross  the 
equator  at  a  point  1000  miles  west.  When  a 
southward  impulse  is  given  to  the  air  it  fol- 
lows, to  some  extent,  the  same  law,  so  that  to 
one  standing  on  the  equator  the  northern 
trade  wind  will  blow  from  the  northeast  and 
the  southern  trade  wind  from  the  southeast. 

Owing  to  the  fact  that  the  air  rises  in  the 
heated  zone  there  is  always  a  region  of  calms 
at  this  point  where  there  is  no  wind  and  no 
rain.  There  are  two  other  regions  of  calms  in 
the  ocean,  one  at  the  north  at  the  tropic  of 
Cancer  and  another  at  the  south  near  the 
tropic  of  Capricorn.  As  has  been  stated,  there 
are  currents  flowing  back  in  the  upper  regions 
at  the  equator  north  and  south,  and  these  are 
called  the  upper  trades — the  lower  currents 
being  called  the  lower  trades.  These  upper 
trades  gradually  fall  till  they  reach  the  tropic 
of  Cancer  on  the  north,  where  the  lower  part 
of  the  current  stops  and  bends  back  toward  the 


fit  mow*.  87 

equator,  now  becoming  a  part  of  the  lower 
trade  wind.  This  causes  a  calm  at  that  point 
where  it  turns.  The  upper  parts  of  this  cur- 
rent continue  on,  in  a  northerly  and  southerly 
direction,  on  the  surface  until  they  meet  with 
the  cold  air  of  the  north  and  south  polar 
regions,  where  there  is  a  conflict  of  the  ele- 
ments— as  there  always  is  when  cold  and  warm 
currents  meet. 

The  only  point  where  the  trade  wind  has 
free  play  is  in  the  South  Indian  Ocean,  and 
this  is  called  the  "  heart  of  the  trades." 

If  the  whole  globe  were  covered  with  water 
there  would  be  a  more  constant  condition  of 
temperature ;  but  owing  to  the  great  difference 
between  the  land  and  water,  both  as  to  altitude 
and  the  ability  to  absorb  and  radiate  heat,  we 
have  all  of  these  varied  and  complicated  con- 
ditions of  wind  and  weather.  The  trade 
winds  shift  from  north  to  south  and  vice  versa 
with  the  advancing  and  receding  seasons,  due 
to  the  fact  that  the  earth  has  a  compound 
motion.  It  not  only  revolves  on  its  axis  once 
in  twenty-four  hours,  but  it  rocks  back  and 
forth  once  a  year,  which  is  gradually  changing 
the  direction  of  its  axis;  and  in  addition  to 
these  motions  it  is  traveling  around  the  sun  as 
well. 


CHAPTEK  XI. 

WIND — CONTINUED. 

In  our  last  chapter  we  discussed  the  winds 
that  prevail  in  the  regions  of  the  tropics  called 
trade  winds,  because  they  follow  a  direct 
course  through  the  year,  with  the  exceptions 
noted  in  regard  to  their  shifting  to  the  north 
or  south  with  the  changing  seasons;  we  also 
described  the  phenomena  of  land  and  sea 
breezes,  which  during  certain  seasons  of  the 
year  reverse  their  direction  twice  daily.  We 
will  now  describe  another  kind  of  wind,  called 
monsoons,  that  prevail  in  India. 

India  lies  directly  north  of  the  great  Indian 
Ocean,  and  the  lower  part  of  it  comes  within 
the  tropical  belt  lying  south  of  the  Tropic  of 
Cancer.  During  the  summer  season  here  the 
earth  stores  more  heat  during  the  day  than  it 
radiates  or  loses  during  the  night.  This 
causes  the  wind  to  blow  in  a  northerly  direc- 
tion from  the  sea  both  day  and  night  for  six 
months  each  year,  from  April  to  October. 
During  these  months  the  land  is  continually 
heated  day  and  night  to  a  higher  temperature 
than  the  water  in  the  ocean  south  of  it.  The 
winds  are  probably  not  so  severe  during  the 


Win*.  89 

night  as  through  the  day,  as  the  difference  be- 
tween the  temperature  of  the  land  and  the 
water  will  not  be  so  great  during  the  night; 
and  difference  of  temperature  between  two 
points  usually  means  a  proportional  difference 
in  the  velocity  of  the  wind.  There  is  a  time 
in  the  fall  and  spring,  while  there  is  a  struggle 
betw>en  the  temperature  of  the  land  and  water 
for  supremacy,  when  the  winds  are  variable, 
attended  with  local  storms  somewhat  as  we 
have  them  in  the  temperate  zone.  But  after 
the  sun  has  moved  south  to  a  sufficient  extent 
the  land  of  India  loses  more  heat  at  night  than 
is  stored  up  in  the  day;  hence  the  conditions 
during  the  winter  months  are  reversed,  the 
water  is  constantly  warmer  than  the  land,  and 
there  is  a  constant  wind  blowing  from  the 
land  to  the  ocean,  which  continues  until  April, 
when  after  a  season  of  local  storms  the  condi- 
tions are  established  in  the  opposite  direction. 
These  winds  are  called  "  monsoons." 

The  word  monsoon  is  probably  derived  from 
an  Arabic  word  meaning  "  seasons."  It  is  a 
peculiarity  of  this  monsoon  that  in  summer  it 
blows  in  a  northeasterly  direction  from  the  sea 
and  in  the  winter  in  a  southwesterly  direction 
from  the  land.  This  divergence  from  a  direct 
north  and  south  is  caused  by  the  rotation  of 
the  earth  and  the  explanation  is  the  same  as 
that  we  have  given  for  the  trade  winds. 

In  the  southern  latitudes  there  is  a  com- 


90  feature's 

paratively  constant  condition  of  wind  and 
weather,  because  the  surface  of  the  globe  in 
these  regions  is  mostly  water ;  but  in  the  north, 
where  most  of  the  land  surface  is  located,  we 
have  a  very  different  and  a  very  complicated 
set  of  conditions,  as  compared  with  the  south- 
ern zones. 

The  freaks  of  wind  and  weather  that  we  find 
prevailing  upon  the  North  American  conti- 
nent are  not  so  easily  accounted  for  as  the  phe-* 
nomena  heretofore  discussed.  In  the  north- 
ern part  the  land  reaches  far  up  toward  the 
north  pole,  while  on  the  west  lies  the  Pacific 
Ocean,  which  merges  into  the  Arctic  Ocean  at 
Bering  Strait.  The  climate  of  the  western 
coast  is  affected  by  a  warm  ocean  current  that 
sets  up  as  far  north  as  Alaska,  while  high 
ranges  of  mountains  prevent  the  effects  of  this 
warm  current  from  being  felt  inland  to  any 
great  extent;  all  of  which  helps  to  complicate 
any  theory  that  may  be  advanced  regarding 
changes  of  weather.  Aside  from  the  changes 
of  temperature  that  are  due  to  the  seasons, 
which  are  caused  by  the  oscillating  motion  of 
the  earth  between  the  limits  of  the  Tropic  of 
Cancer  on  the  north  and  the  Tropic  of  Capri- 
corn on  the  south,  there  are  other  changes  con- 
stantly taking  place  in  all  seasons  of  the  year. 
While  it  is  not  difficult  to  account  for  the 
change  of  seasons  and  the  gradual  change  of 
temperature  that  would  naturally  follow — 


mint*.  91 

owing  to  the  difference  of  angle  at  which  the 
sun's  rays  strike  the  earth — it  is  more  difficult 
to  account  for  the  violent  changes  that  occur 
several  times  during  the  progress  of  a  season, 
as  well  as  the  less  violent  ones  that  come  every 
few  days.  In  fact,  it  rarely  happens  that  the 
temperature  is  exactly  the  same  on  any  two 
successive  days  during  the  year.  The  diurnal 
changes  are  easily  accounted  for  by  the  rota- 
tion of  the  earth  on  its  axis  each  day.  But 
there  is  another  class  of  phenomena  with 
which  the  "weather  man"  has  to  struggle 
when  he  is  making  up  a  forecast  of  the 
weather  from  day  to  day. 

In  order  that  we  may  proceed  intelligently, 
let  us  say  a  word  about  the  barometer.  We 
speak  of  high  and  low  barometer,  and  we  make 
the  instrument  with  graduations  marked  for 
all  kinds  of  weather,  which  really  mean  but 
very  little.  The  reading  of  a  single  barometer 
alone  will  give  us  but  a  faint  idea  of  what  is 
really  going  to  happen  from  day  to  day.  But 
if  we  have  a  series  of  barometers  located  at 
different  stations  scattered  all  over  the  conti- 
nent and  connected  at  headquarters  by  tele- 
graph, so  that  we  can  have  the  readings  fnom 
a  whole  series  of  barometers  at  once,  then  it 
becomes  a  very  useful  instrument.  A  barom- 
eter may  read  low  at  one  station  by  the  scale, 
but  may  be  high  with  reference  to  some  other 
barometer  that  reads  very  low. 


92  flature'0  /HMracle0, 

What  is  a  barometer?  If  we  should  take 
a  glass  tube  closed  at  one  end,  the  area  of 
the  cross  section  of  which  is  one  inch  square, 
and  fill  it  with  mercury,  and  while  thus  filled 
plunge  the  open  end  into  a  vessel  of  mercury, 
it  will  be  found  that  the  amount  of  mercury 
remaining  in  the  tube  above  the  level  of  the 
mercury  in  the  vessel  will  weigh  about  fifteen 
pounds,  if  the  experiment  has  been  per- 
formed at  sea-level.  This  will  vary,  however, 
according  to  the  temperature  of  the  air.  Of 
course  barometers  are  tested  when  the  air  is  at 
a  certain  temperature.  If  the  weight  of  mer- 
cury in  the  tube  is  fifteen  pounds,  since  it  is 
sustained  by  the  air  pressing  down  on  the 
mercury  in  the  open  vessel,  it  shows  that  the 
air-pressure  on  that  open  vessel  is  equal  to 
fifteen  pounds  to  the  square  inch.  In  prac- 
tice, of  course,  the  tubes  are  made  very  much 
smaller.  If  the  air  changes  so  that  it  is 
lighter  than  normal  the  mercury  will  fall  in 
the  tube,  because  the  pressure  on  the  mercury 
in  the  open  vessel  is  less  than  fifteen  pounds 
to  the  square  inch.  And,  again,  conditions 
may  arise  that  will  condense  the  air  and  make 
it  for  the  time  being  weigh  more  than  fifteen 
pounds  to  the  square  inch,  in  which  case  the 
mercury  will  rise  in  the  tube.  Thus  it  will  be 
seen  that  the  barometer  will  register  the 
slightest  change  in  air  pressure. 

Let  us  dwell  for  a  moment  on  the  causes  of 


93 


what  are  commonly  called  "changes  of 
weather,"  when  we  will  again  revert  to  the  use 
of  the  barometer. 

The  use  of  the  telegraph  in  connection  with 
the  establishment  of  a  weather  bureau  having 
stations  for  observation  at  convenient  points 
throughout  the  country  has  contributed  much 
to  the  science  of  meteorology.  It  is  found 
that  there  are  areas  of  high  and  low  pressure 
existing  at  the  same  time  in  different  parts  of 
the  country.  These  usually  have  their  origin 
in  the  far  northwest,  and  follow  each  other, 
sweeping  down  the  eastern  side  of  the  Rocky 
Mountains  and  gradually  bending  easterly  and 
from  that  to  northeasterly  by  the  time  they 
reach  the  Atlantic  coast.  The  areas  of  low 
pressure  are  called  cyclones,  while  the  areas  of 
high  pressure  are  called  anti-cyclones.  (By 
cyclone  we  do  not  mean  those  cloud  funnels 
commonly  called  by  that  name  that  form  at 
certain  times  of  the  year  in  certain  sections  of 
the  country  and  produce  such  destruction  of 
life  and  property.  These  storms  are  usually 
confined  to  a  narrow  strip  and  are  short-lived. 
They  arise  undoubtedly  from  local  conditions. 
A  description  of  these  tornadoes  —  for  such  is 
their  true  name  —  will  be  given  in  some  future 
chapter.) 

These  centers  of  high  and  low  pressure  may 
be  several  hundred  miles  apart.  In  the  area 
of  high  pressure,  if  it  is  in  the  winter  season, 


94  IRature'0 

the  weather  is  unusually  clear  and  cold,  and 
generally  clear  and  fairly  cool  at  any  season, 
and  while  there  may  be  some  wind  it  is  not  so 
strong  as  in  the  cyclone  or  low-pressure  center. 
At  this  point  it  will  be  warmer  and  winds  will 
prevail,  with  rain  or  snow,  the  winds  varying 
in  direction  and  intensity  at  a  given  point  as 
the  cyclone  moves  forward.  In  the  center  of 
these  cyclones  and  anti-cyclones  there  will  be 
a  region  of  comparative  calm,  and  the  air  is 
ascending  at  the  center  of  the  area  of  low 
pressure  while  it  is  pouring  in  on  all  sides 
from  the  area  of  high  pressure  where  the  air 
is  compressed  by  a  downward  current  from  the 
upper  regions. 

The  high-pressure  or  anti-cyclone  system 
usually  covers  a  larger  area  than  the  low- 
pressure  system,  where  the  air  is  ascending. 
While  the  air  moves  laterally  from  high  to 
low,  it  does  not  move  in  a  direct  line.  The 
air  movement  outside  of  the  high-pressure 
center  is  usually  not  at  a  very  high  speed,  but 
in  northern  latitudes  in  the  direction  of  the 
hands  of  a  clock.  As  it  circles  around  it 
widens  out  spirally  until  it  reaches  the  edge 
of  a  low-pressure  system,  when  it  bends  in  its 
course  and  moves  in  the  other  direction 
around  this  center,  but  constantly  moving  in- 
ward toward  it  in  a  spiral  form  and  in  a  direc- 
tion that  is  reverse  to  that  of  the  hands  of  a 
clock.  When  the  air  current  comes  within  the 


TOnfc,  05 

influence  of  a  low-pressure  or  cyclonic  system 
the  velocity  of  its  movement  is  very  much  ac- 
celerated until  it  has  moved  into  the  zone  of 
quiet  air  in  the  center,  where  it  is  ascending. 

In  the  upper  regions  of  the  atmosphere 
there  are  counter  currents  flowing  in  the  oppo- 
site direction.  The  downward  flow  at  the  area 
of  high  pressure  compresses  the  air  near  the 
surface  of  the  earth  and  rarefies  it  in  the 
higher  regions  of  the  atmosphere,  while  the 
opposite  effect  is  going  on  over  the  center  of 
low  pressure,  the  air  being  rarefied  nearer  the 
surface  of  the  earth,  but  condensed  above  nor- 
mal in  the  higher  regions  by  the  upward  cur- 
rent, which  causes  an  overflow  back  toward  the 
rarefied  upper  regions  over  the  area  of  high 
pressure. 

It  will  be  observed  that  the  ordinary  storm 
has  a  compound  motion.  The  whole  system 
moves  in  an  easterly  direction,  while  the  winds 
are  blowing  spirally  about  the  storm  center. 
If  we  should  be  in  the  track  of  a  moving  storm 
so  that  its  center  passed  over  us  the  winds  at 
the  beginning  would  blow  in  one  direction  and 
then  there  would  come  a  subsidence  until  it 
had  moved  forward  through  the  quiet  zone, 
when  we  should  feel  the  wind  in  the  opposite 
direction  until  the  area  of  low  pressure  had 
moved  forward  into  the  region  of  high  pres- 
sure. The  velocity  of  the  wind  will  be  deter- 
mined by  the  difference  of  pressure  between 


96  flature'*  /BMracie0* 

the  areas  and  by  the  distance  that  the  areas  of 
high  and  low  pressure  are  apart.  The  steeper 
the  grade  the  more  rapidly  the  fluid  will  flow. 

Let  us  now  have  recourse,  for  a  moment,  to 
Figs.  1,  2,  and  3  in  order  that  the  subject  may 

South. 

(Jpp*r  Air 


Lo»    *_  ^_    High 

FIG.  1. 

be  more  fully  understood.  In  looking  at  these 
diagrams  we  should  imagine  ourselves  looking 
South,  with  the  left  hand  to  the  East. 

Fig.  1  shows  the  general  direction  of  the  air 
movement  between  two  areas — one  of  high 
and  the  other  of  low  pressure.  The  arrows 
show  the  general  direction  of  the  wind.  You 
will  notice  that  in  the  upper  regions  it  blows 
in  an  opposite  direction  from  the  air  move- 
ment on  the  surface  of  the  earth. 

Fig.  2  shows  in  a  general  way  how  the  wind 
moves  spirally  around  both  centers.  Over 
the  area  of  high  pressure  the  air  descends 
spirally  from  the  upper  regions,  circling 
around  a  large  area — it  may  be  one  hundred 
miles  or  more  in  diameter — in  the  direction  of 
the  movement  of  the  hands  of  a  clock. 


But  then  the  wind  at  the  high-pressure  area 
is  lighter  than  it  is  at  the  low,  and  circles  out- 
wardly until  it  finally  moves  off  in  the  direc- 
tion of  a  low-pressure  area,  gradually  bending 
in  the  other  direction  until  finally  it  moves 
the  reverse  of  the  hands  of  a  clock — although 
now  it  is  in  a  smaller  circle,  and  with  a  more 
rapid  motion.  It  moves  spirally  and  up- 
wardly about  the  low-pressure  area  until  it 
reaches  a  point  in  the  upper  air,  where  it  goes 
through  the  same  gyrations  in  an  opposite  di- 


£asf   /        "~^\ 


Wzsf 


rection.  Now  imagine  the  whole  combination 
moving  from  west  to  east  at  an  average  rate  of 
thirty  miles  per  hour,  and  imagine  further 
that  this  system  is  linked  to  other  systems 
that  are  following  along,  and  you  have  some 
idea  of  the  weather  changes  as  they  occur  in 
the  middle  United  States. 


98 


IKtature'0 


By  referring  to  Fig.  3  you  will  see  why 
the  wind  changes  its  direction  when  a  storm 
center  passes  over  any  point,  It  has  not  only 
a  spiral  but  also  a  forward  movement. 


FIG.  3. 

Now  let  us  go  back  to  the  barometer  and  see 
what  part  it  plays  in  predicting  changes  in  the 
weather.  At  the  area  of  low  pressure  the  air 
is  ascending,  as  we  have  seen,  and,  owing  to 
the  peculiar  way  it  ascends — by  circling 
spirally  upward  around  a  region  of  compara- 
tive calm — it  creates  a  partial  vacuum,  which 
is  more  pronounced  in  the  center  of  the  area. 
At  the  area  of  high  pressure  the  air  will  be 
condensed  by  the  descending  current  being 
arrested  by  the  earth.  The  descending  current 
— coming,  as  it  does,  from  the  upper  and 
colder  regions — accounts  for  the  cool  weather 
that  most  always  prevails  at  a  high-pressure 
area.  In  order  to  know  how  great  the  change 
of  weather  is  likely  to  be,  we  must  know  what 
the  readings  of  at  least  two  barometers  are — 


TOfnD,  99 

one  at  the  high-  and  another  at  the  low-pres- 
sure area.  If  the  difference  between  the  read- 
ings of  the  two  barometers  is  very  great,  and 
the  areas  are  comparatively  close  together,  we 
may  expect  the  change  to  be  sudden  and  vio- 
lent. 

"  High  "  and  "  low  "  as  applied  to  a  barom- 
eter are  only  relative  terms.  There  is  no  fixed 
point  on  the  index  of  the  instrument  that  can 
be  said  to  be  arbitrarily  high  or  low.  For  this 
reason  a  single  barometer  is  not  of  much  use. 
If  it  begins  to  fall  from  any  point,  and  falls 
rapidly,  it  indicates  that  an  area  of  a  much 
lower  pressure  is  approaching.  The  same  is 
true  of  a  high-pressure  area,  if  the  barometer 
rises  rapidly  from  any  point. 

If  we  study  the  air  motions  in  these  systems 
sufficiently  to  get  at  least  an  inkling  of  the 
law  of  their  movements,  it  becomes  a  very 
interesting  subject. 

Wind  from  whatever  cause  serves  a  wonder- 
fully useful  purpose  in  the  economy  of  nature. 
Without  wind,  heat  and  moisture  could  not  be 
distributed  over  the  face  of  the  earth  and  our 
globe  would  not  be  a  fit  habitation  for  man. 
How  wonderful  is  the  machinery  of  Nature, 
that  can  first  forge  a  world  into  shape  and 
afterward  decorate  it  with  green  grass  and 
flowers  that  are  watered  by  the  "early  and 
latter  rain"! 


CHAPTEE  XII. 

LOCAL    WINDS. 

There  are  so  many  causes  that  will  produce 
air  motion  that  it  is  often  difficult  to  deter- 
mine just  what  one  is  the  chief  factor  in  caus- 
ing the  direction  of  the  wind  at  any  particular 
time.  There  are  very  many  instances,  how- 
ever, where  the  cause  can  be  traced  without 
difficulty;  many  of  these  have  already  been 
mentioned  and  there  are  many  more  that 
might  be.  Of  course,  as  has  been  often  stated, 
there  is  only  one  remote  cause  for  all  winds, 
and  that  is  the  sun,  coupled  with  the  move- 
ments of  the  earth.  But  there  are  certain 
local  conditions  that  are  continually  modify- 
ing the  phenomena  of  air  movement.  The 
velocity  of  winds  as  they  occur  from  day  to 
day  varies  very  greatly  with  the  height  above 
the  surface  of  the  earth;  ordinarily  the  ve- 
locity at  1000  feet  above  the  earth  will  be  more 
than  three  times  greater  than  it  is  at  50  or  60 
feet  above,  and  even  at  60  feet  the  velocity  is 
much  greater  than  at  the  surface  of  the  earth. 
This  is  due  partly  to  the  retarding  effect  of 
100 


Xocal  TOn&s,  101 


friction  caused  by  contact  of  the  air  with  the 
earth's  surface,  but  more  particularly  by  trees, 
inequality  of  surface,  and  other  obstructions 
on  the  earth. 

There  is  a  variety  of  wind  called  mountain 
winds  that  arise  from  different  causes.  As 
has  been  stated  in  a  former  chapter,  under 
ordinary  conditions  the  air  is  more  dense  at 
sea-level  than  at  any  point  above,  and  the  den- 
sity is  constantly  changing  from  denser  to 
rarer  the  higher  we  ascend.  Suppose  at  a  cer- 
tain point,  say  halfway  up  a  mountain  side, 
the  air  has  a  certain  density,  and  if  it  is  at 
rest  the  lines  of  equal  density  or  pressure  will 
seek  a  level,  just  as  water  would  under  the 
same  conditions.  Suppose  we  start  at  a  given 
point  on  the  side  of  a  mountain  and  run  out 
on  a  level  till  we  are  100  feet  in  a  perpendicu- 
lar line  above  the  side  of  the  mountain,  the  air 
contained  within  those  lines  will  be  in  the 
shape  of  a  triangle.  If  now  the  sun  shines 
upon  the  side  of  the  mountain  the  air  is 
warmed  and  expands  according  to  a  well- 
known  law,  and  the  amount  of  expansion  will 
depend  upon  the  depth  of  the  volume  of  air; 
hence  the  point  of  greatest  expansion  in  our 
figure  will  be  where  the  air  is  100  feet  deep, 
and  will  gradually  decrease  as  we  go  toward 
the  mountain  till  we  come  to  the  point  where 
our  horizontal  line  makes  contact  with  the 
mountain  side.  At  that  point,  of  course, 


102  matured  /^trades* 

there  is  no  expansion,  because  there  is  no 
depth  of  air;  and  the  effect  will  be  that  the 
expanded  air  will  overflow  toward  the 
mountain,  and  be  deflected  up  its  sloping  side. 
If  we  apply  this  same  principle  to  the  whole 
mountain  side  we  can  see  that  there  will  be, 
during  the  day,  a  constant  current  of  air  flow- 
ing up  the  mountain.  As  night  comes  on  this 
upward  movement  will  cease  and  there  will  be 
a  season  of  quiet  until  the  earth  has  become 
colder  than  the  air,  and  we  have  a  phenomenon 
of  exactly  the  opposite  kind,  when  the  air  con- 
tracts instead  of  expands,  which  produces  a 
downward  current  from  the  mountain  top. 

These  currents  are  as  regular  at  certain  sea- 
sons of  the  year  as  the  land  and  sea  breeze. 
Of  course,  they  may  be  obliterated  for  the 
time  being,  by  the  presence  of  a  stronger  wind 
due  to  some  other  cause,  such  as  during  the 
prevalence  of  a  storm.  In  some  of  the  regions 
of  California  hottest  during  the  day  time,  the 
nights  are  made  endurable,  and  even  delight- 
ful, by  the  cool  breezes  that  sweep  down  from 
the  tops  of  the  mountains.  It  often  happens 
that  on  the  shady  side  of  a  high  and  steep 
mountain  where  the  sun's  rays  strike  it  so 
obliquely,  if  at  all,  that  the  earth  will  be  but 
little  heated,  there  will  be  a  vast  mass  of  cold 
air  stored  up.  After  the  valley  has  become  in- 
tensely heated  by  the  sun  there  is  an  ascend- 
ing current  of  air  which  in  turn  causes  a  down 


ILocal  WfnDs.  103 


rush  of  the  cold  body  of  air  from  the  mountain 
side.  These  local  winds  are  frequently  very 
severe,  only  lasting,  however,  for  a  short  time, 
until  an  equilibrium  of  temperature  and  den- 
sity has  been  established.  A  wonderful  exhi- 
bition of  this  sort  of  wind  is  said  to  occur  at 
certain  times  of  the  year  on  the  coast  at  Tierra 
del  Fuego,  where  a  blast  which  they  call  the 
"  Williwaus,"  comes  down  from  the  mountain 
side,  without  warning,  with  such  tremendous 
force  that  no  ship  could  stand  the  strain  if  it 
should  continue  or  any  length  of  time.  For- 
tunately the  shock  does  not  last  more  than 
eight  or  ten  seconds,  when  it  is  followed  by  a 
perfect  calm.  It  is  as  though  a  great  volume 
of  air  had  been  fired  from  some  enormous  can- 
non from  the  top  of  the  mountain  to  the  sea. 
The  water  is  pulverized  into  a  spray  that  is 
driven  in  every  direction. 

Sometimes  these  violent  blasts  occur  in  the 
Alps,  but  from  a  very  different  cause.  Ava- 
lanches of  great  extent  often  take  place  on  the 
sides  of  the  mountains,  when  a  vast  amount 
of  material,  equal  to  three  or  four  hundred 
million  cubic  feet  of  earth,  will  fall  several 
thousand  feet.  Often  an  avalanche  of  this 
kind  will  produce  a  wind,  which  is  confined, 
of  course,  to  a  restricted  area,  that  is  said  to 
be  so  violent  as  to  tear  one's  clothes  into 
shreds.  This  is  not  caused  by  any  difference 
of  temperature,  but  by  a  violent  compression. 


104  matured  dfciracles. 

There  is  a  peculiar  wind  that  occurs  in 
Switzerland,  often,  between  the  months  of 
November  and  March.  These  winds  last  from 
two  to  three  days  and  are  of  great  violence — 
especially  near  the  mountains.  They  are 
warm  and  dry  and  are  caused  by  an  area  of 
low  barometer  and  an  ascending  current  of  air 
occurring  at  some  point  north  of  the  Alps, 
which  causes  the  air  from  Italy  to  flow  over 
the  Alpine  range,  causing  a  tremendous  pre- 
cipitation of  snow  and  rain,  which  not  only 
takes  the  moisture  from  the  air,  but  sets  free 
in  the  form  of  heat  the  energy  that  was  stored 
in  the  process  of  evaporation,  and  this,  to- 
gether with  the  compression  of  the  air  as  it 
flows  down  the  slope  of  the  mountains,  makes 
it  hot  and  dry.  This  wind  is  called  the 
"  Fohn." 

There  is  a  similar  condition  of  things  exist- 
ing on  the  eastern  slope  of  the  Eocky  Moun- 
tains which  has  a  modifying  effect  upon  the 
climate  of  parts  of  Colorado,  Wyoming,  Mon- 
tana, also  extending  up  into  British  America. 
This  wind,  which  is  here  called  "  chinook," 
arises  from  causes  similar  to  those  that  are 
active  in  Switzerland  that  give  rise  to  the 
"  f  ohn  "  wind. 

There  is  a  wind  called  the  "blizzard"  that 
is  felt  most  keenly  in  Montana  and  the  Da- 
kotas  during  the  winter,  which  is  exceedingly 
cold  and  lasts  sometimes  for  a  period  of  100 


ILocal  TNUnto*  105 

hours.  The  temperature  falls  at  times  30  or 
40  degrees  below  zero  and  the  wind  maintains 
a  velocity  of  from  forty  to  fifty  miles  an  hour. 
These  winds  spread  eastward  as  far  as  Illinois, 
but  not  with  the  same  severity,  and  they  move 
southward  to  the  Gulf  of  Mexico,  spreading 
over  the  States  of  Texas  and  Louisiana,  and 
are  there  called  "  northers."  It  is  exceedingly 
dangerous  to  be  caught  in  a  blizzard  in  the 
Dakotas,  where  the  wind  reaches  its  greatest 
velocity  and  the  cold  its  lowest  temperature — 
especially  when  the  wind  is  accompanied,  as  it 
frequently  is,  by  severe  snowing.  By  the  time 
it  reaches  the  Gulf  States  it  is  very  much 
modified  as  to  temperature,  but  it  is  a  very  dis- 
agreeable wind  in  that  portion  of  the  country, 
because  of  the  exceeding  dampness  of  the  air. 
One  would  be  much  more  comfortable  in  dry, 
still  air,  even  if  it  were  many  degrees  below 
zero,  than  in  an  air  freighted  with  moisture, 
although  the  temperature  has  not  fallen  to 
the  freezing  point. 

There  are  hot  winds  called  by  different 
names  according  to  the  localities  in  which 
they  occur.  In  southern  California  at  certain 
seasons  of  the  year  the  inhabitants  are  af- 
flicted with  what  they  call  a  desert  wind  that 
blows  from  the  heated  regions  of  Arizona  to- 
ward the  Pacific  Ocean.  The  temperature 
sometimes  reaches  120  degrees  Fahrenheit,  and 
persons  have  been  known  to  perish  from  the 


106  feature's  /flMracles, 

effects  of  these  hot  winds  in  open  boats  out  on 
the  water  before  they  could  reach  land. 

Hot  winds  prevail  on  the  plains  of  Kansas 
during  the  months  of  July  and  August  that 
are  phenomenal  in  their  intensity,  so  much  so 
that  if  they  were  widespread  and  of  long  con- 
tinuance, like  the  northern  blizzard,  they 
would  be  attended  with  great  loss  of  life  and 
destruction  to  vegetation.  Fortunately,  they 
come  in  narrow  streaks  and  in  most  cases  do 
not  blow  more  than  from  ten  to  thirty  minutes 
at  a  time.  These  hot  belts  are  sometimes  not 
over  100  feet  wide,  and  again  they  are  as  much 
as  500.  They  are  so  hot  and  dry  that  green 
leaves  and  grass  are  rendered  as  dry  as  powder 
in  a  few  minutes.  These  winds  are  probably 
caused  by  the  fact  that  at  this  season  of  the 
year,  when  the  prevailing  wind  is  south- 
westerly, the  air  becomes  heated  to  a  great 
height,  and  are  the  resulting  effect  of  certain 
combinations  of  air  currents  in  the  higher 
regions  of  the  atmosphere  that  force  the  al- 
ready heated  air  toward  the  earth.  As  the  air 
descends  it  is  more  and  more  compressed, 
which  causes  it  to  become  more  and  more 
heated.  We  have  already  described  the  heat- 
ing effect  of  compression  upon  air  as  shown  by 
the  experiment  with  the  fire  syringe.  It  was 
shown  that  air  at  normal  temperature  could  be 
suddenly  compressed  into  so  small  a  space  that 
the  condensed  heat,  which  was  before  diffused 


Xocal  TOnae.  107 


through  the  whole  bulk  of  air  at  normal 
pressure,  was  sufficient  to  cause  ignition.  A 
cubic  yard  of  air  on  the  surface  of  the  earth 
would  occupy  a  much  larger  space  if  carried  a 
mile  above  it.  From  this  it  is  easy  to  see  that 
ff  a  volume  of  air  at  that  height  had  a  temper- 
ature of  TO  or  80  degrees  it  would  be  very  hot 
when  condensed  into  a  very  much  smaller 
volume,  as  it  would  be  if  it  were  forced  down 
to  the  surface  of  the  earth.  These  winds  are 
the  result  of  some  superior  force  that  is  active 
in  the  upper  regions  of  the  atmosphere,  be- 
cause it  is  natural  for  heated  air  to  rise,  and 
this  is  what  happens  when  the  power  that 
forced  it  down  to  the  earth  is  no  longer  active 
to  hold  it  there. 

Reference  has  been  made  in  a  former  chap- 
ter to  tornado  winds;  they  are  rather  excep- 
tional phenomena  and  not  thoroughly  under- 
stood. The  winds  seem  to  blow  in  from  all 
directions  toward  an  area  of  very  low  pressure 
at  a  single  point.  The  spiral  motion  that  is 
common  to  all  cyclones,  in  a  tornado  seems  to 
be  gathered  up  into  a  condensed  form,  like  a 
funnel.  The  direction  of  movement  is  the 
same  as  that  of  the  cyclone  —  that  is,  in  the  re- 
verse direction  to  that  of  the  hands  of  a  watch. 
The  upward  motion  of  the  air  inside  of  the 
funnel  is  at  a  rate  of  over  170  miles  an  hour. 
The  onward  movement  of  the  whole  system  is 
about  thirty  miles  per  hour. 


108  matured  dfcfraclee. 

Tornadoes  occur  with  greater  frequency  in 
the  United  States  than  in  any  other  section  of 
the  globe.  Tornadoes  seldom  occur  in  winter, 
except  perhaps  in  the  Southern  States.  They 
are  more  frequent  in  the  month  of  May  than 
at  any  other  time  during  the  year,  although 
they  occur  sometimes  in  April,  June,  and  July. 

Between  1870  and  1890  about  sixty-five  de- 
structive tornadoes  occurred  in  the  United 
States,  involving  great  loss  of  life  and  prop- 
erty. When  a  tornado  moves  off  the  land  on 
to  the  ocean  it  may  become  what  is  termed  a 
waterspout.  These  probably  never  originate 
on  the  water,  but  after  they  have  once  formed 
may  be  carried  over  the  water  to  a  considera- 
ble distance.  A  tornado  was  never  known  to 
originate  on  the  shores  of  Lake  Michigan,  but 
there  are  a  few  instances  (the  most  notable 
one  being  the  Racine  tornado)  when  they  have 
reached  the  lake  after  having  traveled  from 
some  distant  point  inland. 

The  Eacine  tornado — so  called  because  it  de- 
stroyed a  large  portion  of  that  city — happened 
fifteen  or  more  years  ago.  The  tornado  origi- 
nated about  100  miles  southwest  of  Racine, 
Wis.,  in  northern  Illinois.  The  funnel-shaped 
cloud  passed  over  the  lake,  but  the  tornado 
character  of  the  storm  was  broken  up  before 
it  reached  the  other  shore. 

When  a  tornado  passes  from  land  to  water 
it  becomes  a  waterspout  only  when  the  cloud- 


fcocal  TOnDs,  109 


funnel  hangs  low  enough  and  the  gyratory 
energy  is  sufficiently  great.  There  is  a  great 
pressure  on  the  water  outside  of  the  funnel 
and  almost  a  perfect  vacuum  inside.  This 
latter  fact  contributes  largely  to  the  de- 
structive power  of  the  tornado.  When  a  fun- 
nel is  central  over  a  building  a  sudden  vacuum 
is  created  outside  of  it  and  it  bursts  outwardly 
from  the  internal  air  pressure. 


CHAPTEE  XIII. 

WEATHER    PREDICTIONS. 

To  predict  with  any  great  accuracy  what 
the  weather  will  be  from  day  to  day  is  a  some- 
what complicated  problem,  and,  as  all  of  us 
have  reason  to  know,  weather  predictions 
made  by  those  who  have  the  matter  in  charge 
and  are  supposed  to  know  all  about  it  often 
fail  to  come  to  pass.  The  real  trouble  is  that 
they  do  not  know  all  about  it.  There  are  so 
many  conditions  existing  that  are  outside  of 
the  range  of  barometers,  thermometers,  ane- 
mometers, and  telegraphs  that  no  one  can  tell 
just  when  some  of  these  unknown  factors  will 
step  in  to  spoil  our  predictions. 

In  very  many  cases,  perhaps  in  a  large  ma- 
jority of  them,  the  predictions  made  by  the 
weather  bureau  substantially  come  to  pass. 
It  has  been  stated  in  former  chapters  that  the 
changes  of  weather  accompany  the  movements 
of  what  are  called  cyclones  and  anti-cyclones, 
the  cyclone  being  accompanied  by  low  baro- 
metric pressure  and  the  anti-cyclone  by  a 
higher  one.  The  winds  of  the  cyclone  move 

110 


Weatber  predictions.  m 

spirally  around  the  center  of  lowest  depression 
with  an  upward  trend,  the  motions  being  in  a 
direction  reversed  to  that  of  the  hands  of  a 
clock.  In  the  centers  of  high  pressure  the 
current  is  downward  instead  of  upward  and 
the  direction  of  the  wind  around  it  is  opposite 
to  that  around  the  low-pressure  area.  The 
fundamental  factor  in  predicting  the  weather 
is  the  direction  of  movement  of  these  areas  of 
low  pressure.  In  almost  all  cases  the  direc- 
tion of  movement  is  from  the  west  to  the  east, 
but  not  always  in  a  straight  line.  These 
movements,  however,  are  classified  so  that 
after  the  direction  has  become  established  one 
can  predict  with  considerable  accuracy  as  to 
whether  it  will  move  in  a  curved  or  a  straight 
line.  By  movement  we  do  not  refer  to  the  di- 
rection of  the  wind  at  any  particular  point, 
but  the  onward  movement  of  the  whole 
cyclonic  system,  which  is  usually  from  twenty- 
five  to  thirty  miles  an  hour,  but  in  some  cases 
the  speed  is  much  greater. 

Not  only  does  the  upward  movement  of  the 
whole  system  vary,  but  the  velocity  of  the 
wind  around  any  given  cyclonic  center  varies. 
There  are  about  eleven  classes  of  cyclones  that 
appear  in  the  United  States,  each  class  having 
its  own  path  of  movement  and  origin.  A 
large  number  of  these  appear  to  originate 
north  of  the  Dakotas,  and  move  directly  east 
to  the  Gulf  of  St.  Lawrence.  Three  other 


112  IRature'0  /HMractes, 

classes  originate  on  about  the  same  line,  a  little 
west, — say,  north  of  Montana, — moving  first  in 
a  southeasterly  direction,  passing  over  the  cen- 
ter of  Lake  Michigan  and  bending  northerly 
through  Lake  Ontario  and  finally  landing  in 
the  Gulf  of  St.  Lawrence.  Two  other  classes 
start  at  the  same  point,  one  of  them  going  as 
far  south  as  Cincinnati,  and  the  other  as  far 
south  as  Montgomery,  Ala.,  and  both  turning 
at  these  points  northeasterly  to  the  Gulf  of  St. 
Lawrence.  Two  other  classes  originate  in 
Colorado,  one  moving  in  a  northeasterly  di- 
rection slightly  curved,  and  the  other  directly 
east.  Still  others  have  their  origin  farther 
south  in  the  Gulf  of  Mexico,  and  move  in  a 
northeasterly  direction.  Very  rarely  they 
originate  in  the  Atlantic  east  of  Savannah, 
moving  first  in  a  northwesterly  direction,  but 
finally  bending  to  the  northeast. 

Every  day  there  is  a  weather  map  made  up 
showing  the  locations  of  the  high  and  low 
barometers,  direction  of  wind,  lines  of  equal 
pressure,  as  well  as  those  of  temperature.  By 
study  from  year  to  year  all  of  these  phe- 
nomena have  become  systematized,  so  that  by 
tracing  an  area  of  low  barometer  from  its 
origin  in  its  progress  easterly  it  is  soon  seen 
to  fall  under  one  of  these  classes  and  we  are 
able  to  predict  about  what  its  course  will  be. 
Knowing  the  speed  of  its  movement  as  well  as 
the  velocity  of  wind  and  all  the  conditions  at- 


TJdeatber  predictions.  113 

tending  it,  taken  in  connection  with  the 
weather  conditions  in  the  region  for  which  the 
prediction  is  made,  an  expert  can  ordinarily 
forecast  with  some  degree  of  accuracy.  After 
all  that  can  be  said,  however,  weather  predic- 
tions based  upon  maps  are  and  have  been  far 
from  satisfactory.  One  who  has  been  a  close 
student  of  local  conditions  for  a  number  of 
years  will  often  predict  with  as  great  accuracy 
as  the  weather  bureau.  Areas  of  low  pressure 
are  followed  sooner  or  later  by  a  fall  of  tem- 
perature; this  is  especially  true  in  the  winter 
months.  Sometimes  this  fall  is  very  marked, 
and  then  it  is  called  a  cold  wave.  These  sud- 
den changes  of  temperature  are  not  thor- 
oughly understood,  but  are  supposed  to  be  due 
partly  at  least  to  rapid  radiation  of  heat  into 
the  upper  regions,  as  the  clear  atmosphere 
which  usually  attends  areas  of  high  pressure 
is  favorable  to  such  a  condition.  Undoubt- 
edly, too,  there  are  dynamic  causes,  forcing 
the  colder  air  from  the  upper  regions  to  the 
earth,  when  it  immediately  flows  off  toward  an 
area  of  low  barometer. 

Long-time  predictions  are  purely  guesses. 
They  sometimes  guess  on  the  right  side,  and 
this  gives  them  courage  to  make  another.  It 
is  an  old  saying  that  "  all  signs  fail  in  dry 
weather."  In  time  of  a  drought  it  is  true  that 
the  indications  which  at  ordinary  times  would 
be  surely  followed  by  a  rain  are  of  no  value. 


114  flature's  /HMracIes. 

When  a  season  is  once  established,  either  as  a 
rainy  season  or  a  dry  season,  it  is  likely  to  per- 
sist in  this  character  until  a  change  comes 
that  is  produced  by  the  movement  of  the  sun 
in  its  course  northerly  and  southerly,  and  the 
change  produced  from  this  cause  requires  sev- 
eral weeks  of  time. 

If  accurate  weather  predictions  could  be 
made  for  a  long  time  in  advance,  or  for  even  a 
week,  they  would  be  of  incalculable  value. 
But  it  is  doubtful  if  ever  this  will  be  brought 
about,  as  there  are  too  many  necessarily  hid- 
den factors  which  enter  into  the  calculations. 
If  stations  could  be  established  all  over  the 
oceans  with  sufficient  frequency,  and  an  equal 
number  at  a  sufficient  altitude  in  the  air,  I 
have  no  doubt  that  much  that  is  now  mys- 
terious might  be  made  plain. 


CHAPTER  XIV. 

HOW    DEW    IS    FORMLD. 

Eeader,  did  you  ever  live  in  the  country? 
Were  you  ever  awakened  early  on  a  summer's 
morning  to  "  go  for  the  cows "  ?  Did  you 
ever  wade  through  a  wheat  field  in  June — or 
the  long  grass  of  a  meadow— when  the  pearly 
dewdrops  hung  in  clusters  on  the  bearded 
grain,  shining  like  brilliants  in  the  morning 
sun?  Have  you  not  seen  the  blades  of  grass 
studded  with  diamonds  more  beautiful  than 
any  that  ever  flashed  in  the  dazzling  light  of 
a  ballroom?  If  not,  you  have  missed  a  pic- 
ture that  otherwise  would  have  been  hung  on 
the  walls  of  your  memory,  that  no  one  could 
rob  you  of. 

Everyone  has  noticed  that  at  certain  times 
in  the  year  the  grass  becomes  wet  in  the  even- 
ing and  grows  more  so  till  the  sun  rises  the 
next  day  and  dispels  the  moisture,  and  this 
when  no  cloud  is  seen.  Dew  is  as  old  as  the 
fields  in  which  grass  grows.  It  was  as  fa- 
miliar to  the  ancients  as  it  is  to  us,  and  yet  it 
is  only  about  three-quarters  of  a  century  since 

115 


116  feature's 

the  cause  of  it  has  been  understood.  We  even 
yet  speak  of  the  dew  "  falling  "  like  rain.  In 
former  times  some  scientists  supposed  that  it 
was  a  fine  rain  that  fell  from  the  higher 
regions  of  the  atmosphere.  Others  supposed 
it  to  be  an  emanation  from  the  earth,  while 
still  others  supposed  it  was  an  exudation  from 
the  stars. 

"By  his  knowledge  the  depths  are  broken  up  and  the 
clouds  drop  down  dew  "  (Prov.  iii.  20). 

The  first  experiments  carried  on  in  a  scien- 
tific way  were  by  Dr.  Wells,  a  physician  of 
London,  between  the  years  1811  and  1814. 

Everyone  has  noticed  in  warm  weather  the 
familiar  phenomenon  of  water  condensed  into 
drops  on  the  outside  of  a  pitcher  or  tumbler 
containing  cold  water.  This  condensation  is 
dew.  It  always  forms  when  the  conditions 
are  right,  summer  and  winter.  In  cold 
weather  we  call  it  frost.  It  has  been  stated 
in  a  former  chapter  on  evaporation  that  the 
capacity  of  the  air  for  holding  moisture  in  a 
transparent  form  depends  upon  its  tempera- 
ture. If  the  temperature  is  at  the  freezing 
point  it  will  contain  the  160th  part  of  the  at- 
mosphere's own  weight  as  aqueous  vapor.  If 
it  is  60  degrees  Fahrenheit  the  air  will  retain 
six  grains  of  transparent  moisture  to  the 
square  foot  of  air,  while  at  80  degrees  it  will 
contain  nearly  eleven  grains.  When  the  air 


1bow  Dew  ie  ^formed,  u? 

is  charged  with  this  vapor  to  the  point  of  satu- 
ration (which  point  varies  with  the  tempera- 
ture) a  slight  depression  of  the  temperature 
is  sufficient  to  condense  this  vapor  into  cloud 
or  drops  of  water.  Between  1812  and  1814 
Dr.  Wells  made  a  series  of  experiments  with 
flocks  of  cotton  wool.  He  weighed  out  pieces 
of  equal  weight  and  attached  a  number  of 
them  to  the  upper  side  of  a  board  and  as  many 
more  to  the  lower  side,  and  exposed  it  to  the 
night  air  under  varying  conditions.  One  ex- 
periment was  made  with  a  board  four  feet 
from  the  earth,  so  that  half  of  the  bunches  of 
cotton  faced  the  ground  and  the  other  half  the 
sky.  He  found  upon  weighing  these  after  a 
night's  exposure  under  a  clear  sky  that  the 
cotton  wool  on  top  of  the  board  had  gained 
fourteen  grains  in  weight  from  the  moisture, 
or  dew,  that  had  formed  upon  it,  while  the 
same  amount  of  cotton  on  the  under  side  of 
the  board  had  only  increased  four  grains.  He 
tried  further  experiments  by  making  little 
paper  houses,  or  boxes,  to  cover  a  certain  por- 
tion of  grass  or  vegetation.  He  found  that 
while  there  would  be  a  heavy  dew  on  the  grass 
outside  there  was  little  or  none  within  the  in- 
closure.  These  experiments  were  conducted 
in  various  ways  and  closely  watched  to  see 
that  none  of  the  phenomena  were  in  any  way 
connected  with  falling  rain.  It  has  been  de- 
termined that  substances  like  grass  and  green 


118  Batute's  /UMracles. 

leaves  of  all  kinds,  hay  and  straw,  while  they 
are  poor  conductors  of  heat,  are  excellent 
radiators.  In  another  chapter  we  have  re- 
ferred to  this  quality  of  straw,  that  is  taken 
advantage  of  by  the  inhabitants  of  hot  coun- 
tries in  the  manufacture  of  ice  and  in  our  own 
land  for  storing  it. 

Perhaps  everyone  who  has  lived  in  the  coun- 
try has  noticed  that  on  a  summer's  morning 
when  the  grass  is  laden  with  dewdrops  a  gravel 
walk  or  a  dusty  road  will  be  perfectly  dry. 
This  is  due  to  the  fact  that  the  gravel  will  re- 
tain heat  and  not  radiate  it,  for  a  much  longer 
time  than  grass  or  green  leaves.  Dew  begins 
to  form  upon  the  grass  very  soon  after  the  sun 
is  set  because  the  moment  the  sun's  rays  are 
withdrawn  the  heat  is  rapidly  radiated  by  the 
blades  of  grass,  which  cools  the  earth  under  it 
and  the  air  above  and  surrounding  it,  so  that 
if  the  air  is  anywhere  near  the  moisture  satu- 
ration point  on  cooling  at  the  surface  of  the 
ground  it  will  readily  give  up  a  part  of  its 
moisture,  which  condenses  in  drops  upon  the 
blades  of  grass. 

If  the  night  is  still  and  clear  and  there  is 
much  moisture  in  the  air,  the  dew  will  be 
heavy,  but  if  the  night  is  cloudy  there  will  be 
little  or  no  dew  formed.  The  clouds  form  a 
screen  between  the  earth  and  the  upper  regions 
of  the  atmosphere,  which  prevents  the  heat 
from  radiating  to  a  sufficient  extent  to  form 


1bow  Dew  fa  formed.  119 

dew.  For  the  same  reason  no  dew  will  form 
under  a  light  covering  spread  over  the  ground 
even  at  some  distance  above  it.  The  covering 
acts  as  a  screen,  which  prevents  the  heat  from 
radiating  to  the  dew  point.  From  what  has 
gone  before  it  will  be  seen  that  if  the  atmos- 
phere is  not  charged  with  moisture  up  to  the 
point  of  saturation  it  will  require  a  greater 
amount  of  depression  of  temperature  to  cause 
condensation,  and  this  is  why  we  usually  have 
heavier  dews  in  June  when  the  air  is  more 
highly  charged  with  moisture  than  we  do  in 
August  when  it  is  dry.  This  also  accounts  for 
the  ice  clouds,  called  cirrus,  being  formed  so 
high  up  in  the  atmosphere  during  dry  weather. 
There  is  so  little  moisture  in  the  air  that  it  re- 
quires a  very  great  difference  of  temperature 
to  cause  condensation  to  take  place,  and  the 
necessary  depression  is  not  reached  in  these 
cases  except  at  an  altitude  of  several  miles. 

Dr.  Wells  has  shown  that  if  we  take  the 
reading  of  two  thermometers  on  a  clear  sum- 
mer night,  one  of  them  lying  on  the  grass  and 
the  other  suspended  two  feet  above  it,  we  shall 
find  that  the  one  lying  on  the  grass  will  read 
8  or  10  degrees  lower  than  the  one  suspended 
in  the  air.  If  the  night  is  still  there  will  be 
a  cold  stratum  of  air  next  to  the  earth,  which 
will  not  tend  to  diffuse  itself  to  a  very  great 
degree  and  dew  will  form.  If,  however,  it  is 
cloudy  or  the  wind  is  blowing  there  is  rarely 


120  matured  /liMraclea, 

any  formation  of  dew.  The  reason  in  the  for- 
mer case,  as  we  have  explained,  is  that  the 
radiated  heat  is  held  down  to  the  earth  in  a 
measure,  and  in  the  latter  case  there  is  a  con- 
stant change  of  air;  so  that  in  either  case  no 
part  of  it  is  allowed  to  cool  down  sufficiently 
to  precipitate  moisture. 

It  is  a  curious  fact  that  often  there  will  be 
a  heavier  dew  under  the  blaze  of  a  full  moon 
on  a  clear  night  than  at  any  other  time.  The 
moon  has  no  screens  about  it  of  any  kind  to 
obstruct  the  free  radiation  of  heat.  It  is  sup- 
posed to  be  a  dead  cinder  floating  in  space  and 
not  surrounded  by  an  atmosphere,  so  that  the 
sun's  rays  have  full  effect  upon  it  during  the 
time  it  is  exposed  to  them,  and  at  that  time  it 
becomes  heated  to  a  temperature  of  something 
like  750  degrees  Fahrenheit.  For  half  the 
month,  say,  the  sun  is  shining  continuously 
upon  all  or  a  part  of  it.  In  other  words,  the 
days  and  nights  of  the  moon  are  about  two 
weeks  long.  The  moon  does  not  revolve  upon 
its  own  axis  like  the  earth,  therefore  the  same 
side  or  a  portion  of  it  is  exposed  to  the  sun 
for  14  days.  During  the  time  that  the  moon 
is  in  the  earth's  shadow  it  is  supposed  to  fall 
to  187  degrees  below  zero,  which  is  219  degrees 
below  the  freezing  point.  When  the  moon  is 
full  and  is  heated  up  to  over  700  degrees  there 
is  sufficient  heat  radiating  from  it  to  be  felt 
sensibly  upon  the  face  of  the  earth,  and  it 


1bow  Dew  is  fformefc,  121 

would  be  felt  if  it  were  not  for  the  great  en- 
velope of  atmosphere  and  its  attendant  c^oud 
formations  that  surround  the  earth.  There 
are  but  few  days  in  summer  when  there  is  not 
a  haze  in  the  atmosphere,  although  we  call  the 
sky  clear,  which  intensifies  the  light  and  gives 
everything  a  warmer  tone.  The  heat  coming 
from  a  full  moon  on  a  clear  night  is  absorbed 
in  causing  the  aqueous  vapors  that  are  partly 
condensed  in  the  higher  regions  of  the  atmos- 
phere, to  be  reabsorbed  into  transparent  vapor. 
This  clears  away  the  heat  screen  in  the  atmos- 
phere and  allows  radiation  to  go  on  more 
rapidly  at  the  earth's  surface,  and  thus  cools 
it  to  a  greater  extent  when  the  moon  is  shin- 
ing brightly  than  when  it  is  dark  and  in  the 
shadow  of  the  earth. 

As  we  have  already  mentioned,  the  cold  that 
is  produced  by  radiation  through  the  blades  of 
grass  and  other  radiating  substances  may  be 
indicated  by  placing  one  thermometer  on  the 
ground  and  fixing  another  at  some  point  in  the 
air.  Sometimes  the  difference  is  very  marked, 
amounting  to  as  much  as  20  or  30  degrees.  If 
under  these  conditions  a  cloud  floats  over- 
head, forming  a  heat  screen,  its  presence  will 
be  readily  noticed  by  a  rise  in  the  thermom- 
eter. Radiation  into  the  upper  regions  of  the 
atmosphere  is  checked,  which  causes  a  sudden 
rise  in  the  temperature  near  the  surface  of  the 
earth.  By  taking  advantage  of  this  principle 


122  nature^  iflMracles, 

of  heat  radiation  from  the  earth's  surface  it 
is  a  very  easy  matter  to  protect  tender  vegeta- 
tion from  even  quite  a  severe  frost,  if  it  occurs 
in  the  early  fall,  by  a  slight  covering,  such  as 
thin  paper.  The  paper  will  act  as  a  heat 
screen  and  in  a  measure  prevent  the  heat  from 
radiating  from  the  earth  immediately  under 
it.  Frost — which  of  course  is  but  frozen  dew 
— at  this  season  of  the  year  will  form  on  a  still 
autumn  night,  although  the  atmosphere  at 
some  distance  above  the  ground  is  some  de- 
grees above  the  freezing  point.  The  reason 
for  this  will  be  obvious  when  we  consider  the 
facts  that  have  been  set  forth  concerning  the 
power  of  radiation  to  produce  cold. 

It  has  been  estimated  by  meteorologists  that 
the  amount  of  water  condensed  upon  the  sur- 
face of  the  earth  in  the  form  of  dew  amounts 
to  as  much  as  five  inches,  or  about  one-seventh 
of  the  whole  amount  of  moisture  that  is  evap- 
orated into  the  air.  It  will  thus  be  seen  that 
dew  performs  an  important  part  in  supporting 
vegetation. 

The  same  operation  in  nature's  great  work- 
shop that  forms  the  dews  of  summer  creates 
the  frosts  of  winter.  The  moisture  in  cold 
weather  is  condensed  the  same  as  in  warm. 
When  it  is  condensed  at  the  surface  of  the 
earth  we  have  the  phenomenon  of  frost,  but 
when  condensed  in  the  upper  regions  of  the 
atmosphere  we  have  that  of  snow. 


1bow  Dew  10  fformefc.  123 

Heat  radiation  from  the  earth  goes  on  in 
winter,  which  is  evidenced  by  the  fact  that  a 
thick  covering  of  snow  is  a  great  benefit  to 
vegetation  as  a  protection  against  the  in- 
jurious effects  of  frost.  The  writer  has  seen 
flowers  blooming  abundantly  at  an  altitude  of 
12,000  feet  above  the  sea-level,  protected  only 
by  the  friendly  shelter  of  a  snowbank.  In 
some  cases  the  blooming  flowers  were  in  actual 
contact  with  the  snow.  By  experiment  it  has 
been  determined  that  the  earth  under  a  thick 
coating  of  snow  is  usually  warmer  by  nine  or 
ten  degrees  than  the  air  immediately  above  the 
snow  covering. 


CHAPTEE  XV. 

HAILSTONES    AND    SNOW. 

A  hailstone  is  a  curious  formation  of  snow 
and  ice,  and  most  of  the  large  hailstones  are 
conglomerate  in  their  composition.  They  are 
usually  composed  of  a  center  of  frozen  snow, 
packed  tightly  and  incased  in  a  rim  of  ice,  and 
upon  this  rim  are  irregular  crystalline  forma- 
tions jutting  out  in  points  at  irregular  dis- 
tances. Frequently,  however,  we  find  them 
very  symmetrically  formed  as  to  outline,  and 
the  snow  centers  are  almost  without  exception 
round.  Hailstones  and  hailstorms  differ  in 
different  climates,  but  they  are  more  pro- 
nounced in  the  torrid  than  in  the  temperate 
zone.  Historians  give  accounts  of  hailstones 
of  enormous  size;  the  very  large  hailstones 
being  undoubtedly  aggregations  of  single 
stones  that  have  been  thrown  together  and 
congealed  in  the  clouds  during  their  fall  to 
the  earth. 

It  is  recorded  that  on  July  4,  1819,  hail- 
stones fell  at  Baconniere  measuring  fifteen 
inches  in  circumference,  and  very  symmetri- 

124 


Ibaflstones  anfc  Snow,  125 

cally  formed,  with  beautiful  outline.  Hail- 
stones in  India  are  said  to  be  very  large — from 
five  to  twenty  times  larger  than  those  in  Eng- 
land or  America — seldom  less  than  walnuts 
and  often  as  large  as  oranges  and  pumpkins. 
It  is  recorded  that  in  1826,  during  a  hailstorm 
at  Candeish,  the  stones  perforated  the  roofs 
of  houses  like  cannon  shot,  and  that  a  single 
mass  fell  that  required  several  days  to  melt, 
weighing  over  100  pounds.  It  is  further  re- 
corded that  on  May  8,  1832,  a  conglomerate 
mass  of  hailstones  fell  in  Hungary  a  yard  in 
length  and  nearly  two  feet  in  thickness.  Still 
another  instance  is  recorded  of  a  hailstone 
having  fallen  in  1849  of  nearly  twenty  feet  in 
circumference.  This  hailstone  is  said  to  have 
fallen  upon  the  estate  of  Mr.  Moffat  of  Ord. 
We  will  only  ask  our  readers  to  listen  to  one 
more  hailstone  story,  in  which  it  is  related 
that  during  the  reign  of  Tippoo,  sultan,  a  hail- 
stone fell  as  large  as  an  elephant.  Undoubt- 
edly one  of  two  things  was  true  regarding  this 
latter  story;  it  was  either  a  very  large  hail- 
stone or  a  very  small  elephant.  The  historian 
fails  to  give  the  size  of  the  elephant.  There 
is  no  doubt,  however,  but  that  hailstones  may 
adhere  and  form  large  masses  owing  to  the 
violent  agitation  of  the  elements  that  always 
attends  a  hailstorm. 

Hailstorms  are  almost  universally  attended 
by  constant  and  heavy  thunder  and  lightning, 


126  matured 

together  with  violent  winds.  They  usually 
occur  on  a  very  hot  day,  and  when  the  air  is 
filled  to  saturation  with  moisture.  When  this 
is  the  case  a  column  of  air  is  very  highly 
heated  at  some  point,  when  it  ascends  with 
great  force  into  the  upper  regions  of  the  at- 
mosphere to  a  greater  altitude  than  is  com- 
mon in  the  case  of  ordinary  thunderstorms. 
Here  it  meets  with  an  intensely  cold  body  of 
air,  when  it  is  suddenly  condensed  and  readily 
frozen  as  soon  as  condensed,  which  not  only 
forms  hailstones,  but  sets  free  the  energy  that 
has  been  carried  up  in  the  moisture  globules. 
This  results  in  frequent  electrical  discharges, 
causing  great  waves  of  condensed  and  rarefied 
air,  which,  in  the  rarefied  portions,  produces 
still  more  intense  cold;  so  that  we  have  the 
conditions  for  a  mighty  struggle  between  the 
elements,  which  is  intensified  by  a  constant 
and  terrific  electric  cannonade.  Undoubtedly 
there  are  also  whirlwinds  in  the  cloud,  similar 
to  those  that  sometimes  visit  the  earth,  which 
would  tend  to  gather  up  the  hailstones  and 
aggregate  them  into  large  masses.  It  is  a 
mighty  battle  between  the  moisture-laden, 
superheated  air,  ascending  from  the  surface  of 
the  earth,  and  the  powers  residing  in  the  upper 
regions  of  cold.  Nature  is  constantly  strug- 
gling to  find  an  equilibrium  of  her  forces,  and 
a  hailstorm  is  only  one  of  the  little  domestic 
flurries  that  take  place  when  she  is  setting  her 


•toafletonee  anfc  Snow.  i2/3r 

house  to  rights.  Hailstorms  are  usually  con- 
fined to  very  narrow  limits,  and  they  can  pre- 
vail on  a  grand  scale  only  in  hot  climates, 
where  we  have  the  conditions  for  wide  differ- 
ences of  temperature  between  the  upper  and 
lower  regions  of  the  atmosphere;  and,  also, 
where  the  conditions  are  favorable,  for  an 
enormous  amount  of  absorption  of  moisture 
into  the  atmosphere. 

When  snow  is  formed  in  the  atmosphere, 
the  conditions  are  quite  different  from  those 
of  a  hailstorm;  it  is  usually  in  a  lower  plane 
of  the  atmosphere,  and  there  is  no  violent  com- 
motion, as  is  the  case  with  the  latter.  A  vol- 
ume of  air  laden  with  moisture  comes  in  con- 
tact with  a  colder  volume  of  air,  when  conden- 
sation takes  place,  as  in  the  case  of  rain,  except 
that  the  moisture  is  immediately  frozen.  In 
this  case  both  volumes  of  air  may  be  below  the 
freezing  point,  but  one  is  very  much  colder 
than  the  other.  If  the  snow  reaches  the  earth 
it  will  be  because  the  air  is  below  the  freezing 
point  all  the  way  down.  Snow  is  formed  at 
all  seasons  of  the  year.  We  may  have  a  snow- 
storm on  a  high  mountain  when  we  have  ex- 
treme heat  at  sea-level. 

In  summer  time  of  course  the  snow  melts  as 
soon  as  it  falls  into  a  stratum  of  air  with  a 
temperature  above  the  freezing  point,  and  con- 
tinues its  journey  from  that  point  as  raindrops 
instead  of  siiowflakes.  In  the  formation  of  a 


128  mature'*  dfcfracles, 

snowflake  Nature  does  some  of  her  most  beau- 
tiful work.  A  snowflake  first  forms  with  six 
ice  spangles,  radiating  from  a  common  center. 
Shorter  ones  form  on  these  six  spokes,  stand- 
ing at  an  angle  of  about  sixty  degrees,  on  each 
side  of  each  spoke,  of  such  length  and  arrange- 
ment as  to  form  a  symmetrical  figure  or 
flower.  They  do  not  always  take  the  same 
form,  but  follow  the  same  laws  that  govern  the 
formation  of  ice  crystals.  The  structure  of  a 
snowflake  may  be  often  found  upon  a  window 
pane  of  a  frosty  morning.  Here,  however,  the 
free  arrangement  of  the  parts  of  a  snow  crys- 
tal are  interfered  with  by  its  contact  with  the 
window  pane,  but  while  floating  gently  in  the 
air  there  is  the  utmost  freedom  for  the  play  of 
nature's  forces  as  they  apply  to  the  work  of 
crystallization. 

The  difference  in  structure  of  snowflakes  is 
chiefly  due  to  the  conditions  under  which  they 
are  formed.  If  the  moisture  is  frozen  too 
rapidly  the  molecular  forces  that  are  active  in 
crystallization  do  not  have  time  to  carry  out 
the  work,  in  its  completeness  of  detail,  as  it 
will  where  the  freezing  process,  as  well  as  the 
condensing  process,  goes  on  more  slowly. 


CHAPTEK  XVI. 

METEORS. 

Meteors  are  the  tramps  of  interplanetary 
space.  They  sometimes  try  to  steal  a  ride  on 
the  surface  of  the  earth,  but  meet  with  certain 
destruction  the  moment  they  come  within  the 
aerial  picket  line  of  our  world's  defense 
against  these  wandering  vagrants  of  the  air. 
They  have  made  many  attempts  to  take  this 
earth  by  storm,  as  it  were,  and  many  more  will 
be  made.  They  fire  their  missiles  at  us  by  the 
millions  every  year  with  a  speed  that  is  in- 
credible, but  thanks  to  the  protecting  influ- 
ence of  the  great  ocean  of  air  that  envelops 
our  globe  they  become  the  victims  of  their  own 
velocity. 

Meteors  or  shooting  stars  are  as  old  as  the 
earth  itself,  and  they  are  the  material  of  which 
comets  are  made.  Before  it  was  determined 
what  these  meteors  or  shooting  stars  were, 
many  theories  were  promulgated  as  to  their 
origin.  One  was  that  they  were  masses  of 
matter,  large  and  small,  projected  by  volcanic 
action  from  the  face  of  the  moon  with  such 
violence  as  to  be  brought  within  the  attraction 

129 


130  matured  d&fracles. 

of  the  earth.  Others  supposed  them  to  be  the 
effect  of  certain  phosphoric  fluids  that  ema- 
nated from  the  earth  and  took  fire  in  the  upper 
regions  of  the  atmosphere.  This,  however, 
was  mere  speculation  and  without  any  scien- 
tific basis  of  fact.  Anyone  who  has  been  an 
observer  of  shooting  stars  will  have  learned 
that  there  are  certain  periods  of  the  year  when 
they  are  more  numerous  than  at  other  times; 
notably  in  August  and  November.  Then 
again  there  are  longer  periods  of  many  years 
apart.  By  persistent  observation  it  has  been 
established  that  there  are  great  numbers  of 
schools  or  collections  of  cosmic  matter  that  fly 
through  interplanetary  space,  having  definite 
orbits  like  the  planets.  Any  one  of  these  col- 
lections may  be  scattered  through  millions  of 
miles  in  length.  A  comet  is  simply  one  of 
these  wandering  collections  of  meteoric  stones 
having  a  nucleus  or  center  where  the  particles 
are  so  condensed  as  to  give  it  a  reflecting  sur- 
face something  like  the  planets  or  the  moon. 
This  enables  us  to  see  the  outline  of  the  comet 
to  the  point  where  the  fragments  of  matter  be- 
come so  scattered  that  they  are  no  longer  able 
to  reflect  sufficient  light  to  reach  our  eyes. 
The  fringe  of  a  comet,  however,  may  extend 
thousands  or  even  millions  of  miles  beyond  the 
borders  of  luminosity. 

There  is  scarcely  a  day  or  night  in  the  year 
when  more  or  less  of  these  meteoric  stones  do 


/toeteors.  *31 

not  come  within  the  region  of  our  atmosphere, 
and  when  this  happens  the  great  velocity  at 
which  they  travel  is  the  means  of  their  own 
destruction.  They  become  intensely  heated 
by  friction  against  the  atmosphere  just  as  a 
bullet  will  when  fired  from  a  gun — only  to  a 
greater  extent  owing  to  the  greater  velocity. 
They  disintegrate  into  dust  which  floats  in  the 
air  for  a  time,  when  more  or  less  of  it  is  pre- 
cipitated upon  the  surface  of  the  earth.  Dis- 
integrated meteors,  or  star  dust,  as  they  are 
sometimes  called,  are  often  brought  down  by 
the  rain  or  snow.  Most  of  the  shooting  stars 
that  we  observe  are  very  small,  resembling  fire- 
flies in  the  sky,  but  once  in  a  while  a  very 
large  one  is  seen  moving  across  the  face  of  the 
heavens,  giving  off  brilliant  scintillations  that 
trail  behind  the  meteor,  making  a  luminous 
path  that  is  visible  for  some  seconds.  These 
brilliant  manifestations  are  due  to  one  of  two 
causes.  Either  there  is  a  very  large  mass  of 
incandescent  matter  or  else  they  are  so  much 
nearer  to  us  than  in  ordinary  cases  that  they 
appear  larger.  It  is  more  likely,  however, 
that  it  is  due  to  the  former  cause  rather  than 
the  latter,  from  the  fact  of  its  apparently  slow 
movement  as  compared  with  the  smaller  shoot- 
ing stars.  It  has  been  determined  by  observa- 
tion that  the  average  meteor  becomes  visible 
at  a  point  less  than  100  miles  above  the  earth's 
surface.  It  was  found  as  far  back  as  1823  that 


132  lftature'0 

out  of  100  shooting  stars  twenty-two  of  them 
had  an  elevation  of  over  twenty-four  and  less 
than  forty  miles;  thirty-five,  between  forty 
and  fifty  miles;  and  thirteen  between  seventy 
and  eighty  miles.  It  was  determined  by  Pro- 
fessor  Herschel  that  out  of  sixty  observations 
of  shooting  stars  the  average  height  of  their 
first  appearance  was  seventy-eight  miles  and 
their  disappearance  was  at  a  point  fifty-three 
miles  above  the  earth. 

It  is  a  matter  of  history,  however,  that 
sometimes  these  meteoric  stones  descend  to 
the  surface  of  the  earth  before  they  are  en- 
tirely disintegrated.  A  fine  specimen  of  this 
kind  is  to  be  seen  in  the  Smithsonian  Institu- 
tion. There  are  over  forty  specimens  of  these 
aerolites  (air-stones)  in  the  British  Museum, 
labeled  with  the  times  and  places  of  their 
fall.  Instances  of  falling  to  the  earth  are  so 
rare  that  there  is  little  to  fear  from  these  wan- 
dering missiles  of  the  air.  We  do  not  remem- 
ber a  case  where  life  or  property  has  suffered 
from  the  fall  of  a  meteor. 

This  brings  us  to  the  consideration  of  the 
part  which  the  great  air  envelope  surrounding 
the  earth  plays  as  a  protection  against  many 
outside  influences.  For  instance,  if  it  were 
not  for  the  air,  millions  of  these  meteoric 
stones  would  be  showered  upon  our  earth  every 
year  and  at  certain  times  every  day,  which 
would  render  the  earth  untenable  for  human 


133 


existence.  We  should  be  at  the  mercy  of  those 
wandering  comets  whose  fringes  strike  our  at- 
mosphere more  or  less  deeply  at  frequent  in- 
tervals. It  is  not  impossible  that  the  earth 
may  at  some  time  pass  directly  through  one, 
and  yet  there  is  little  danger  that  in  such  a 
case  there  would  be  more  than  an  unusual  dis- 
play of  celestial  fireworks. 

From  the  facts  that  have  been  above  stated 
it  will  be  apparent  to  anyone  that  the  number 
of  these  meteoric  stones  in  the  air  is  being 
constantly  reduced  by  their  constant  collision 
with  the  atmosphere  and  consequent  reduction 
to  ashes  or  dust.  Another  conclusion  is  that 
the  earth  must  be  gradually,  but  imperceptibly 
perhaps,  increasing  in  size  on  account  of  the 
constant  settling  upon  its  surface  of  meteoric 
dust. 


CHAPTEE  XVII. 

THE    SKY    AND    ITS    COLOB. 

In  the  chapters  on  light  in  Vol.  II.  it  will 
be  stated  that  we  see  all  objects  by  a  reflected 
light,  except  those  that  are  self-luminous, 
such  as  the  sun  or  any  other  source  of  light. 
We  see  the  moon  and  many  of  the  planets 
entirely  by  reflection.  There  are  myriads 
of  smaller  objects,  too  small  to  be  seen 
as  such,  even  under  a  microscope,  that  still 
have  a  power  to  reflect  light  that  is  sensible  to 
our  vision.  The  air  surrounding  the  globe  is 
literally  filled  with  these  microscopic  light  re- 
flectors. They  serve  to  give  us  a  diffused 
light  which  enables  us  to  see  clearly  all  visible 
objects.  We  have  all  noticed  the  effect  of  a 
single  electric  arc  light,  situated  at  a  distance 
from  any  other  source  of  light,  and  how  it 
casts  extremely  dark  shadows  and  very  high 
lights ;  so  much  so  that  it  is  difficult  to  see  an 
object  perfectly  in  this  light,  because  the  part 
of  an  object  that  is  under  the  direct  rays  of 
the  lamp  is  so  highly  illuminated  that  the 
shadow,  by  comparison,  has  the  effect  of 

134 


anfc  its  Color*  135 

simply  a  dark  blot  without  form  or  shape. 
Many  of  you  have  noticed  in  a  country  village, 
where  the  streets  are  lighted  with  electric  arc 
lamps,  what  a  difference  there  is  in  the  illumi- 
nating effect  between  a  clear  and  a  foggy 
night.  When  there  is  a  fog,  or  when  the 
clouds  hang  low  down,  we  get  a  reflection 
from  these  which  tends  to  diffuse  and  soften 
the  powerful  light  rays  that  are  sent  out  by 
these  lamps.  This  effect  is  especially  notice- 
able when  the  night  is  only  moderately  foggy. 
Each  globule  of  moisture  floating  in  the  air 
becomes  a  reflector  of  light,  and  by  myriads  of 
reflections  and  counter  reflections  the  light 
(which  on  a  clear  night  is  concentrated)  is 
diffused  over  a  large  area,  producing  an  illu- 
mination which  for  practical  purposes  is  far 
superior  to  that  produced  on  a  clear  night. 
When  the  latter  condition  prevails  the  rays  of 
light  are  so  intense  on  objects  immediately 
surrounding  the  lamps  that  one  is  blinded;  so 
that  the  places  which  are  in  shadow  seem 
darker  than  they  would  be  if  there  were  no 
light  at  all.  The  only  way  to  prevent  this 
effect  is  to  have  the  lights  so  close  together 
that  there  will  be  cross  lights,  which  tend  to 
break  up  the  intensity  of  the  shadows.  This 
principle  of  light  diffusion  is  taken  advantage 
of  to  produce  an  even  illumination  in  stores 
that  are  lighted  only  on  one  or  two  sides. 
This  is  effected  by  a  series  of  prisms  or  reflect- 


136  future's 

ing  surfaces  that  are  cast  upon  the  panes  of 
glass. 

If  now  there  were  no  atmosphere — or,  to 
state  it  differently — if  there  were  no  floating 
substances  in  the  atmosphere,  the  sun  would 
produce  an  effect  upon  the  earth  similar  to 
that  of  a  single  electric  light.  The  lights 
would  be  extremely  high,  and  the  shadows  ex- 
tremely dense.  To  one  looking  off  into  space, 
the  sky,  instead  of  having  the  blue  appearance 
that  we  see,  would  have  the  effect  of  looking 
into  a  deep,  dark  abyss  without  illumination. 

Tyndall  has  shown  us  by  a  beautiful  experi- 
ment that  if  there  be  in  a  glass  tube  a  mixture 
of  gases  related  to  each  other  in  a  certain  way 
chemically,  they  will  combine  into  small 
globules  or  particles  similar  to  moisture  in  the 
.  air.  If  now  a  beam  of  light  is  thrown  upon 
this  tube  and  a  dark  screen  put  behind  it,  we 
shall,  in  the  beginning  of  the  experiment, 
simply  see  the  dark  screen.  As  soon,  however, 
as  the  molecules  of  the  gases  have  combined 
in  sufficient  numbers  to  produce  particles  of 
sensible  size  we  begin  to  have  a  reflection  of 
light  from  them,  the  color  of  which  is  con- 
stantly changing  as  the  combining  particles 
grow  in  size.  At  a  certain  stage  in  its  prog- 
ress the  color  which  the  mixture  of  gases 
assumes  is  a  beautiful  azure  blue,  rivaling  in 
purity  the  finest  skies  of  Greece  or  southern 
Italy. 


Gbe  Sfc£  anfc  its  Color.  137 

The  sun  is  the  great  lamp  that  illuminates 
the  world,  while  the  atmosphere,  which  is  filled 
with  particles  of  various  substances,  becomes 
the  shade  of  the  lamp  which  diffuses  and 
softens  the  light  and  gives  it  its  color  tones, 
whether  of  warmth  or  coldness.  We  could 
not  well  do  without  the  reflected  light  of  the 
sky.  The  poetry  of  life  would  be  sadly 
marred.  The  beautiful  effects  of  color  and 
purity  of  tone  would  be  wanting.  We  need 
to  bathe  in  light  as  much  as  in  water,  and  the 
character  of  the  light  is  almost  as  important 
as  the  character  of  the  water.  Imagine  a 
world  with  an  atmosphere  devoid  of  all  sub- 
stances that  would  in  any  way  reflect  light  or 
give  to  it  softness  or  color  tone.  Imagine  a 
sun  or  a  moon  without  visible  rays — for  with- 
out a  reflecting  atmosphere  there  would  be 
none.  Imagine  a  sky  that  was  no  sky  at  all, 
but  only  a  dark  void,  with  no  protecting  vault. 
Think  of  the  shadows,  so  dark  that  you  could 
see  nothing  in  them.  These  would  be  some  of 
the  effects  that  would  come  from  an  atmos- 
phere that  had  no  sky  substance  in  it. 
Imagine  the  world  lighted  by  one  great  arc 
light.  The  reflex  action  upon  the  race  living 
in  such  a  light  would  be  anything  but  desira- 
ble. The  world  would  develop  into  an  arc- 
light  civilization — if  one  can  imagine  what 
that  would  be  like;  certainly  one  of  intensely 
violent  contrasts.  Look  on  this  picture  and  let 


138  feature's  dfoiracles* 

UM  be  thankful  for  the  blue  sky  and  golden 
sunsets. 

"  But,"  you  ask,  "  why  is  the  sky  blue?  " 
In  one  of  the  chapters  on  the  subject  of 
light  in  Vol.  II.  the  properties  of  soap  bubbles 
are  discussed.  It  is  shown  that  when  a  film 
is  stretched  across  the  mouth  of  a  tumbler 
held  in  a  position  so  that  the  film  is  perpen- 
dicular, by  the  action  of  gravity  (the  moisture 
constantly  falling  to  the  lower  part  of  the  film) 
it  will  continually  grow  thinner,  and  hori- 
zontal bands  of  color  will  appear  upon  it, — 
first  red,  then  followed  by  the  other  colors  of 
the  solar  spectrum,  ending  with  violet. 

It  is  also  stated  that  every  color  of  light  has 
a  definite  wave  length.  Where  a  band  of  blue 
color  appears  upon  the  film  we  know  that  its 
thickness  is  right  for  the  wave  length  of  that 
particular  color  which  is  reflected  from  the 
back  of  the  film  to  the  eye.  If  we  could  con- 
ceive the  blue  vault  of  the  heavens  to  be  half 
a  sphere  of  a  soap  bubble,  the  color  that  the 
sky  would  appear  to  us  (if  the  light  could  be 
thrown  upon  it  from  beneath)  would  be  deter- 
mined by  the  thickness  of  this  film.  If  the 
film  was  1-156,000  of  an  inch  the  sky  would  be 
red  instead  of  blue.  To  reflect  the  other 
colors  the  film  would  have  to  grow  thinner  for 
each  color,  in  the  progression  from  red  to 
violet.  The  color  of  the  sky  is  determined  by 
a  light-reflection  from  minute  globules  of 


Cbe  Sfcs  anD  its  Color.  139 


moisture  floating  in  the  air.  If  the  sky  is 
blue,  then  the  globules  must  be  of  the  right  di- 
ameter to  reflect  that  color.  The  various  tints 
and  colorings  of  the  sky  are  determined  by 
what  is  found  in  the  atmosphere,  and  this  is 
the  reason  why  skies  differ  in  coloring  and 
tone  in  different  sections  of  the  globe.  The 
finest  skies  are  probably  found  in  semi-tropical 
regions  like  southern  Italy,  Greece,  and  Cali- 
fornia. 

In  1892  I  visited  Greece  in  the  early  part  of 
June.  In  crossing  the  Adriatic,  from  Brin- 
disi  to  Patras  in  Greece,  the  route  was  through 
the  Ionian  Islands  that  are  grouped  along  the 
southwestern  shore  of  Albania.  The  sky  was 
without  a  cloud,  and  its  beautiful  blue  color 
was  reflected  in  the  waters  of  the  Adriatic,  and 
I  never  shall  forget  the  impression  made  upon 
my  senses  when  we  first  came  in  sight  of  the 
mountains  on  the  west  coast  of  Albania.  At 
this  point  they  rise  abruptly  from  the  water 
and  are  colored  with  that  peculiar  azure  haze, 
mixed  with  a  shading  of  warmth,  which  is  an 
effect  that  distance  gives  in  the  classic  atmos- 
phere of  old  Greece.  The  effect  upon  the  be- 
holder is  to  intoxicate  the  senses  and  to  fill 
him  with  that  deliciously  poetic  feeling  that 
always  comes  when  standing  in  the  presence 
of  the  sublime  in  nature.  It  was  not  the 
mountains  themselves  that  produced  the  effect, 
for  I  had  seen  grander  than  these;  but  it  was 


d  /JlMracle0. 

the  sky  on  the  mountains.  When  we  look  at  a 
distant  mountain  it  seems  to  be  partly  hidden 
by  a  peculiar  haze  that  is  the  color  of  the  sky 
at  that  time;  we  are  really  looking  at  the 
mountain  through  a  portion  of  the  sky. 
While  in  Athens  I  took  a  trip  to  the  top  of 
Mount  Pentelicus,  which  separates  the  plains 
of  Athens  on  the  south  from  those  of  Mara- 
thon on  the  north.  From  the  summit  of  this 
mountain  we  have  a  most  wonderful  view  of 
the  archipelago  of  the  ^Egean  Sea — a  beauti- 
ful map  of  blue  water  and  brown  islands  that 
melt  together  in  the  distance.  At  our  feet  lay 
the  historic  plains  of  Marathon,  and  in  the  dis- 
tance rose  the  snow-capped  peaks  of  Mount 
Olympus.  It  is  doubtful  if  the  world  fur- 
nishes a  more  beautiful  combination  of  ocean, 
island,  continent,  and  sky  than  can  be  seen 
from  Mount  Pentelicus.  Myriads  of  brown 
islands  set  in  the  bluest  of  water — graceful  in 
outline  and  multiform  in  shape — jutting 
headlands  and  land-locked  harbors — strong  in 
color  and  outline  in  the  immediate  fore- 
ground, but  gradually  melting  together  in  the 
distance,  the  brown  becoming  bluer  and  the 
blue  a  softer  blue  till  the  whole  is  lost  on  the 
horizon  in  a  sky  that  shades  back  to  the  zenith 
in  an  ever-changing  azure  that  for  purity  of 
tone  baffles  all  description. 

What  wonder  that  a  people  born  under  such 
skies  and  whose  eyes  have  feasted  on  such 


Cbe  S&B  ant)  ft*  Colon 


beauties  in  nature  should  conceive  and  execute 
suth  a  masterful  work  of  art  as  the  Par- 
thenon! While  the  variation  of  landscape, 
the  stretch  of  water  filled  with  islands,  and  the 
mountains  capped  with  eternal  snow  were  a 
prominent  part  of  the  picture,  it  was  the  sky 
with  its  beautiful  color-tones  that  after  all 
gave  it  its  wonderful  charm. 

The  skies  in  a  northern  latitude  are  colder 
and  grayer,  due  to  the  fact  that  nearly  always 
there  is  a  certain  degree  of  condensation  of 
moisture  existing,  which,  while  it  does  not 
take  the  form  of  a  cloud,  still  gives  a  toning 
to  the  sky. 

There  is  no  doubt  but  that  the  color-tones 
of  the  sky  have  an  influence  upon  the  charac- 
ter and  temperament  of  the  people  who  live 
under  them.  Under  semi-tropical  skies  the 
poetic  nature  is  more  strongly  appealed  to, 
and  a  man  is  more  likely  to  be  controlled  by 
his  dreamy  imaginings  than  his  cold  calcula- 
tions. We  find  this  latter  characteristic  pre- 
vailing to  a  greater  or  less  extent  among  the 
people  who  live  under  colder  and  sterner  skies. 
If  all  these  qualities  or  influences  could  be 
combined  in  the  right  way,  the  race  would  be 
stronger  intellectually  and  in  other  ways.  It 
is  always  dangerous  to  a  race  of  people  to  be 
developed  along  certain  lines  only.  The  de- 
velopment should  be  symmetrical.  The 
strongest  men  are  not  those  who  are  simply 


142  lftature'0 

coldly  intellectual,  neither  those  who  are 
simply  emotional  and  sentimental,  but  those 
in  whom  heart,  mind,  and  soul  are  so  related 
that  each  one  of  these  elements  re-enforces 
and  strengthens  the  others. 

At  certain  seasons  of  the  year  and  in  certain 
localities  it  is  not  uncommon  to  have  wonder- 
fully beautiful  displays  of  coloring  upon  the 
skies  and  clouds  at  sunset.  The  question  is 
often  asked  why  we  do  not  see  these  displays 
at  other  times  in  the  day  than  at  sunrise  and 
at  sunset — for  the  same  effects  are  seen  in  the 
morning,  but  they  are  not  noticed  so  often,  be- 
cause to  do  so  would  interfere  with  the  habits 
of  the  average  man  and  woman. 

The  reason  for  this  change  of  coloring  is 
the  angle  at  which  the  sun's  rays  strike  the 
clouds  of  an  evening  sky,  which  are  reflected 
to  our  eyes.  When  the  sun  is  high  in  the 
heavens  it  shines  against  the  back  of  the 
clouds,  from  the  point  of  view  of  a  person 
standing  on  the  surface  of  the  earth.  It  also 
shines  a  shorter  distance  through  the  air  at 
midday  than  at  sunset.  At  sunset  the  rays 
are  able  to  shine  on  the  under  side  of  a  cloud, 
especially  if  it  is  high  in  the  air.  The  mois- 
ture globules  of  which  the  cloud  is  made  up 
are  much  larger  than  the  transparent  ones 
that  are  uncondensed  and  just  as  they  were 
when  released  in  the  process  of  evaporation. 

As  we   have   already  seen,   the   reflections 


Hbe  Sfcg  ant>  its  Colon  143 

from  these  minute  globules  give  us  the  blue 
coloring  of  the  sky  and  are  very  much  smaller 
in  diameter  than  a  globule  that  is  able  to  re- 
flect the  red  ray.  When  these  small  globules 
are  condensed  into  cloud  a  great  number  are 
combined  into  one  globule,  and  they  are  of  all 
sizes,  from  the  globule  of  evaporation  to  that 
of  the  raindrop  when  precipitation  takes  place. 
We  have,  then,  in  the  various  stages  of  cloud 
formation  all  conditions  present  for  reflecting 
the  various  colors  and  combinations  of  colors 
that  are  found  in  the  solar  spectrum.  Hence 
it  is  that,  under  certain  conditions  of  atmos- 
phere and  cloud  formation,  we  see  at  sunset 
painted  upon  the  sky  those  wonderful  combi- 
nations of  colors,  more  beautiful  and  delicate 
in  shading,  more*  various  in  combination  and 
purer  of  tone,  than  any  artist,  however  cun- 
ning his  fingers  or  brilliant  his  pigments,  has 
ever  been  able  to  truthfully  reproduce.  Even 
when  the  sky  is  cloudless  it  often  assumes  a 
brilliant  hue,  which  is  partly  a  reflection  from 
invisible  moisture  globules  and  partly  due  to 
floating  particles  of  dust  that  may  have  been 
driven  up  from  the  surface  of  the  earth,  or 
may  be  the  ashes  of  meteorites  disintegrated 
by  contact  with  the  air. 

Some  years  ago,  commencing  in  August, 
1883,  there  was  a  wonderful  exhibition  of  red 
skies  at  sunset  that  lasted  for  several  hours 
after  twilight  ordinarily  disappears.  This 


144  Nature's 

phenomenon  ran  through  a  period  of  several 
weeks,  gradually  fading  away.  It  was  after- 
ward determined  that  these,  displays  were  oc- 
casioned by  small  particles  of  ashes  or  dust 
floating  high  in  the  air,  that  were  thrown  off 
from  the  volcanic  eruption  of  Krakatoa  in 
the  Island  of  Java.  By  the  general  circula- 
tion of  the  air  the  ashes  were  carried  to  all 
parts  of  the  world,  making  a  circuit  of  the 
earth  in  from  twelve  to  thirteen  days — which 
showed  a  velocity  of  over  eighty  miles  an  hour. 
This  is  an  instance  of  the  high  velocity  of  the 
air  currents  in  the  upper  regions  of  the  atmos- 
phere. The  reason  why  the  illumination  ex- 
tended so  late  in  the  night  was  because  of  the 
great  height  that  these  particles  of  dust  at- 
tained. The  higher  the  reflecting  surfaces  are 
in  the  air  the  longer  they  may  be  seen  after 
sunset.  Ordinary  twilight  is  caused  by  a  re- 
flection of  sunlight  from  the  upper  air;  and 
from  its  duration  as  ordinarily  observed  it  is 
estimated  that  the  reflection  does  not  proceed 
from  a  point  more  than  thirty-six  miles  high. 
In  the  higher  latitudes  the  twilight  is  long, 
from  the  fact  that  the  sun  does  not  go  directly 
down,  and  if  we  go  far  enough  north  the  whole 
night  is  twilight.  In  the  tropical  regions  the 
twilight  is  shorter  than  at  any  other  point  on 
the  globe  for  reasons  that  are  obvious.  The 
sun  there  goes  directly  down  and  is  soon  hid- 
den behind  the  earth. 


tlbe  S&B  anfc  its  Colon  145 

There  are  other  optical  effects  to  be  seen 
sometimes  on  the  horizon  somewhat  resem- 
bling twilight.  The  "  aurora  borealis  "  (north- 
ern lights),  which  we  describe  in  Vol.  III.,  is 
seen  in  the  northern  skies  at  certain  times, 
and  has  very  much  the  appearance  of  twilight 
in  some  of  its  phases.  It  is  constantly  chang- 
ing, however,  and  is  easily  distinguished  by 
anyone  who  has  observed  both.  These  ap- 
pearances are  undoubtedly  electrical.  There 
is  another  phenomenon  seen  in  the  arctic 
regions  that  causes  a  band  of  white  light  to 
appear  on  the  horizon  called  "  ice  blink,"  and 
it  is  caused  by  the  reflections  from  the  great 
icebergs  that  abound  in  that  region. 

Curious  optical  effects  are  sometimes  ob- 
served a  little  after  sunset  in  the  form  of 
streamers  or  bands  of  light  that  shoot  up  into 
the  sky,  sometimes  to  a  great  height.  These 
are  undoubtedly  due  to  cloud  obstructions  that 
partially  shut  off  the  sun's  rays  from  a  part  of 
the  sky,  but  allow  it  to  shine  with  greater  bril- 
liancy in  the  path  of  these  bands  of  light. 

It  will  be  seen  from  the  foregoing  that  the 
sky  in  all  of  its  phases  is  a  product  of  sunlight 
and  the  substances  that  float  in  the  air,  in- 
cluding moisture,  not  only  in  the  invisible 
state,  but  in  all  the  stages  of  condensation,  as 
well  as  particles  of  floating  dust. 


CHAPTER  XYIIL 

LIQUID    AIR. 

Air,  like  water,  assumes  the  liquid  form  at 
a  certain  temperature.  Water  boils  and 
vaporizes  at  212  degrees  Fahrenheit  above 
zero,  while  liquid  air  boils  and  vaporizes  at 
312  degrees  below  zero. 

Heat  and  cold  are  practically  relative  terms, 
although  scientists  talk  about  an  "absolute 
zero  "  (the  point  of  no  heat),  and  Professor 
Dewar  fixes  this  point  at  461  degrees  Fahren- 
heit below  zero.  Others  have  estimated  that 
the  force  of  the  moon  during  its  long  night  of 
half  a  month,  is  reduced  in  temperature  to  six 
or  seven  hundred  degrees  below,  which  is  far 
lower  than  Professor  Dewar's  absolute  zero. 
However  this  may  be,  to  an  animal  that  is  de- 
signed to  live  in  a  temperature  of  70  or  80 
degrees  Fahrenheit,  any  temperature  below 
zero  would  seem  very  cold.  If,  however,  we 
were  adapted  to  a  climate  where  the  normal 
temperature  was  312  degrees  Fahrenheit  below 
zero,  we  should  be  severely  burned  if  we  should 
sit  down  upon  a  cake  of  ice.  Such  a  climate 

146 


Xfquto  Bit.  1*7 

would  be  impossible  for  animal  existence,  for 
the  reason  that  there  would  be  no  air  to 
breathe,  since  it  would  all  liquefy. 

Liquid  air  is  not  a  natural  product.  There 
is  no  place  on  our  earth  cold  enough  to  pro- 
duce it.  If  the  moon  had  an  atmosphere 
(which  it  probably  has  not)  it  would  liquefy 
during  the  long  lunar  night,  for  heat  radiates 
very  rapidly  from  a  planet  when  the  sun's  rays 
are  withdrawn  from  it. 

As  you  have  already  surmised,  liquid  air  is 
a  product  of  intense  cold.  Any  method 
that  will  reduce  the  temperature  of  the  air 
to  312  degrees  Fahrenheit  below  zero  will 
liquefy  it.  Great  pressure  will  not  do  this, 
for  we  may  compress  air  in  a  strong  vessel 
until  the  pressure  on  every  square  inch  of  the 
vessel  is  12,000  pounds,  or  six  tons,  and  still  it 
will  not  liquefy  unless  the  temperature  is 
brought  down  to  the  required  degree  of  cold- 
ness. If  this  is  done  it  will  change  from  a 
gas  to  a  liquid,  but  will  occupy  as  much  space 
as  before,  if  it  is  condensed  to  a  pressure  of 
six  tons  to  the  square  inch. 

Until  twenty  years  ago  it  was  supposed  that 
oxygen  and  atmospheric  air  (the  latter  a  mix- 
ture of  oxygen  and  nitrogen)  were  fixed  gases 
and  could  not  be  liquefied.  In  1877,  it  is  said 
that  Eaoul  Pictet  obtained  the  first  liquid 
oxygen,  but  only  a  few  drops.  About  fifteen 
years  later  Professor  Dewar  of  the  Koyal  In- 


148  matured  /llMractes* 

stitution,  London,  succeeded  in  liquefying  not 
only  oxygen  but  atmospheric  air.  And  be- 
sides liquefying  the  air  he  made  ice  of  it. 

In  1892  I  visited  London,  where  I  met  Pro- 
fessor Dewar,  who  invited  me  to  witness  an 
exhibition  of  the  manufacture  of  liquid  oxy- 
gen— and  incidentally  liquid  air — at  the  Eoyal 
Institution.  To  me  it  was  a  most  wonder- 
fully interesting  event.  I  saw  air,  taken  from 
the  room,  gradually  liquefy  in  a  small  glass 
test  tube  open  at  the  top.  When  the  tube  was 
withdrawn  from  the  refrigerating  chamber  it 
boiled  by  the  heat  of  the  room,  and  rapidly 
evaporated.  We  lighted  a  splinter  of  wood 
and  blew  it  out,  leaving  a  live  spark  on  the  end 
of  it,  and  held  it  over  the  mouth  of  the  tube, 
knowing  that  if  anything  like  pure  oxygen 
were  evaporating  the  splinter  would  relight 
and  blaze  (an  old  experiment  with  oxygen 
gas).  At  first  the  splinter  would  not  relight, 
because  the  evaporating  gases  were  a  mixture 
of  oxygen  and  nitrogen  in  the  proportions  to 
form  air.  But  owing  to  the  fact  that  nitro- 
gen evaporates  sooner  than  oxygen,  a  second 
trial  was  successful,  for  the  splinter  imme- 
diately began  to  blaze,  showing  that  the  gas 
evaporating  then  was  pure,  or  nearly  pure, 
oxygen. 

When  the  liquid  oxygen  was  poured  into  a 
saucer  and  brought  into  proximity  with  the 
poles  of  a  powerful  magnet  the  liquid  imme- 


Bit.  149 

diately  rushed  out  of  the  saucer  and  clung  to 
the  magnet  poles;  showing  that  oxygen  is 
magnetic. 

Since  that  time  other  experimenters  have 
succeeded  in  making  liquid  air  on  a  compara- 
tively large  scale,  and  the  process  is  simple 
when  we  consider  some  of  the  old  methods. 

Mr.  Tripler  of  New  York,  who  has  made 
liquid  air  in  great  quantities,  does  it  substan- 
tially as  follows:  First,  he  compresses  air  to 
about  2500  pounds  to  the  square  inch.  Of 
course  the  air  is  very  hot  when  it  is  first  com- 
pressed because  all  the  air  in  the  tank  has  been 
reduced  in  bulk  about  166  times,  and  all  the 
heat  that  was  in  the  whole  bulk  of  air  is  con- 
centrated into  one-166th  of  the  space  it  occu- 
pied before  it  was  compressed.  It  is  166  times 
hotter.  There  are  two  sets  of  pipes  running 
from  the  compressor  to  a  long  upright  tank 
called  the  liquefier.  These  pipes  pass  through 
running  water,  so  that  the  compressed  air  is 
quickly  cooled  down  to  the  temperature  of  the 
water  (about  50  degrees  Fahrenheit).  The 
pipes — at  least  one  set  of  them — run  the  whole 
length  of  the  liquefier,  and  most  likely  are 
coiled.  This  set  of  pipes  contains  the  air  to 
be  liquefied.  A  second  set  of  pipes  runs  to  the 
bottom  of  the  liquefier,  where  there  is  a  valve. 
By  opening  this  valve  a  jet  of  compressed  air 
is  allowed  to  play  on  the  other  set  of  pipes, 
when  intense  cold  is  produced  by  the  sudden 


150  matured  jfllMracles. 


expansion  of  the  air.  This  cold  air  rus^s  up 
around  the  pipe  containing  the  air  to  be  lique- 
fied and  escapes  at  the  top,  thus  absorbing  the 
heat  until  the  temperature  is  reduced  to  312 
degrees  below  zero.  Then  the  air  liquefies  and 
runs  into  a  receptacle,  where  it  may  be  drawn 
off  at  pleasure. 

It  will  be  seen  that  a  large  part  of  the  com- 
pressed air  is  wasted  in  cooling  the  remainder 
sufficiently  to  liquefy. 

The  use  to  which  liquid  air  may  be  put,  ad- 
vantageously, is  an  unsolved  problem;  but  no 
doubt  it  will  have  a  place  in  time.  All  great 
discoveries  do.  Electricity  had  to  wait  a  long 
time  for  recognition  ;  but  what  a  part  it  plays 
now  in  the  everyday  life  of  the  whole  civilized 
world  ! 

Curious  effects  are  produced  by  this  intense 
cold.  Meat  may  be  frozen  so  hard  that  it  will 
give  off  a  musical  tone  when  struck.  Here  is 
a  pointer  for  the  seeker  of  novelties  in  the  line 
of  musical  instruments. 

Liquid  air  furnishes  a  beautiful  illustration 
of  the  fact  that  a  burning  gas  jet  is  continu- 
ally forming  water  as  well  as  giving  out  heat 
and  light.  If  we  put  liquid  air  into  a  tea 
kettle  and  hold  it  over  a  gas  jet,  ice  will  form 
on  the  bottom  from  the  water  created  by  the 
flame,  and  it  will  freeze  so  hard  that  the  flame 
will  make  no  impression  upon  it,  other  than 
to  make  the  ice  cake  grow  larger. 


Xiquto  2Ur*  151 

Although  liquid  air  is  not  found  in  nature, 
and  is  therefore  called  an  artificial  product,  it 
is  produced  by  taking  advantage  of  natural 
law.  Without  the  intellect  of  man  it  never 
would  have  been  seen  upon  this  earth;  and  the 
same  may  be  said  concerning  many  things  in 
our  world,  both  animate  and  inanimate.  The 
genius  of  man  is  God-like.  He  lifts  the  veil 
that  shrouds  the  mysteries  of  nature,  and  here 
he  comes  in  very  touch  with  the  mind  of  the 
Infinite.  Man  interprets  this  thought  through 
the  medium  of  natural  law,  and  lo,  a  new 
product ! 

How  much  life  would  have  been  robbed  of 
its  charm  and  interest  if  all  these  things  had 
been  worked  out  for  us  from  the  beginning! 
For  there  is  no  interest  so  absorbing  and  no 
pleasure  so  keen  as  that  of  pursuit  when  the 
pursuer  is  reaching  out  after  the  hidden 
things  that  are  locked  up  in  Nature's  great 
storehouse.  From  time  to  time  she  yields  up 
her  secrets,  little  by  little,  to  encourage  those 
who  love  her  and  are  willing  to  work,  not  only 
for  the  pleasure  of  the  getting,  but  for  the 
highest  and  best  good  of  their  fellows. 


WATER. 


CHAPTEK  XIX. 

RIVEKS    AND    FLOODS. 

Water  covers  such  a  large  proportion  of  the 
earth's  surface  and  is  such  an  important  fac- 
tor in  the  economy  of  nature  that  it  becomes  a 
matter  of  interest  to  study  the  process  of  its 
distribution.  Water  is  to  our  globe  what 
blood  is  to  our  bodies.  A  constant  circulation 
must  be  kept  up  or  all  animal  and  vegetable 
life  would  suffer.  Here,  as  in  every  other 
operation  of  nature,  the  sun  is  the  great  heart 
and  motive  power  that  is  active  in  the  distri- 
bution of  moisture  over  the  face  of  the  globe. 

The  total  annual  rainfall  on  the  whole  sur- 
face of  the  earth  amounts  to  about  28,000 
cubic  miles  of  water.  Only  about  ene-fourth 
of  this  amount  ever  reaches  the  ocean,  but  it 
is  either  absorbed  for  a  time  by  animal  and 
vegetable  life  or  lifted  through  the  process  of 
evaporation  into  the  air  as  invisible  moisture, 
when  it  is  carried  over  the  region  of  rainfall 
and  there  condensed  into  water  and  falls  back 

152 


IRfvers  an&  ffloofcs*  153 

upon  the  earth — only  to  go  through  the  same 
operation  again.  The  whole  surface  of  the 
earth  is  divided  into  drainage  areas  that  lead 
either  directly  through  rivulets  and  rivers  to 
the  ocean,  or  into  some  land-locked  basin, 
where  it  either  finds  an  outlet  under  ground  or 
is  kept  within  bounds  through  the  process  of 
evaporation,  the  same  as  is  the  case  with  our 
great  oceans.  In  North  America  the  amount 
of  drainage  area  that  has  no  outlet  to  the 
ocean  amounts  to  about  3  per  cent,  of  the  whole 
surface.  In  other  countries  the  percentage  of 
inland  drainage  is  much  larger.  The  great 
Salt  Lake  in  Utah  is  an  instance  where  there 
is  no  outlet  for  the  water  except  through  the 
medium  of  evaporation.  Inasmuch  as  all 
rivers  and  streams  contain  a  certain  propor- 
tion of  salt, — especially  in  such  strongly  alka- 
line land  regions  as  the  Great  Basin  of  the 
North  American  continent, — these  inland 
lakes  in  time  become  saturated  with  this  and 
other  mineral  substances. 

Salt  is  constantly  being  carried  into  the 
lake  by  the  water  of  the  stream  that  feeds  it, 
and  the  water  is  continually  being  evaporated, 
leaving  the  salt  behind.  This  process  has 
been  going  on  in  the  valley  of  Utah  for  so  long 
a  period  that  17  per  cent,  of  the  contents  of  the 
lake  is  salt.  The  Humboldt  Eiver  in  Nevada, 
which  empties  into  a  small  lake  of  the  same 
name,  and  lies  at  the  foot  of  the  Humboldt 


154  flature'0 

Mountains,  is  said  to  have  an  underground 
outlet.  This  must  be  the  case,  because  the 
area  of  the  lake  is  very  small  as  compared  with 
Salt  Lake,  while  the  river  that  feeds  the  latter 
is  very  small  compared  with  the  one  that  flows 
into  the  former.  That  is  to  say,  in  the  one 
case  a  very  small  stream  empties  into  a  large 
lake,  while  in  the  other  case  a  much  larger 
stream  feeds  a  very  small  lake.  Besides, 
Humboldt  Lake,  unlike  the  Great  Salt  Lake, 
is  said  to  be  a  fresh- water  lake;  if  it  had  no 
outlet  it  would  become  in  time  saturated  with 
salt.  The  largest  body  of  water  in  the  world 
having  no  outlet  to  the  ocean  is  the  Caspian 
Sea,  on  the  border  between  Asia  and  Kussia 
in  Europe,  it  being  180,000  square  miles  in 
extent. 

Where  rivers  empty  into  large  bodies  of 
water,  such  as  the  great  chain  of  lakes  on  the 
northern  border  of  the  United  States  (and 
these  lakes  have  an  outlet  connecting  one  with 
the  other,  and  finally  by  a  river  to  the  ocean) 
a  constant  circulation  is  being  kept  up,  and 
the  water  remains  fresh.  Owing  to  the  fact, 
however,  of  the  great  evaporating  surface 
that  these  lakes  afford,  there  is  a  greater  dis- 
proportion between  the  rainfall  upon  the 
drainage  area  tributary  to  these  lakes,  and  the 
amount  of  discharge  through  the  St.  Law- 
rence Kiver,  than  would  be  the  case  with  a 
river  that  was  not  connected  with  a  system  of 


IRivers  anfc  ffloofcs*  15^ 

lakes.  The  amount  of  rainfall  upon  the  area 
drained  by  the  Mississippi  Kiver  during  one 
year  amounts  to  about  614  cubic  miles  of 
water,  while  the  discharge  at  the  mouth  of  the 
Mississippi  Eiver  is  only  about  154  cubic 
miles.  The  difference  between  the  two  figures 
has  been  carried  up  by  the  process  of  evapora- 
tion or  stored  in  vegetation.  These  figures 
vary  considerably,  however,  with  different 
years. 

The  proportion  of  rainfall  to  discharge  will 
vary  greatly  in  different  rivers  from  other 
causes  than  having  a  large  evaporating  sur- 
face. This  variation  is  due  to  the  difference 
in  the  ability  of  the  soil  to  retain  water  after 
a  rainfall.  In  some  drainage  areas  the  ground 
is  more  or  less  impermeable  to  water,  and  in 
this  case  the  water  runs  readily  off,  causing  a 
sudden  rise  in  the  river;  and  as  suddenly  it 
reaches  the  low-water  mark.  In  other  drain- 
age areas  the  ground  is  very  permeable  to 
water,  so  that  the  rain  penetrates  to  a  greater 
depth  into  the  earth,  where  it  is  held,  and  by 
a  slow  process  drains  into  the  rivers,  while 
much  more  of  it  is  carried  off  by  evaporation 
and  into  vegetation  than  is  the  case  in  the 
drainage  district  before  mentioned. 

The  courses  of  rivers  are  determined  by  the 
topography  of  the  country  through  which  they 
flow.  The  sinuous  windings,  that  are  found 
to  be  a  characteristic  of  nearly  all  rivers,  are 


156  nature's  /liMracles. 

caused  by  the  water,  through  the  force  of 
gravity,  seeking  the  lowest  level,  and  avoid- 
ing obstructions,  which  they  can  flow  around 
more  easily  than  remove. 

Great  rivers  often  change  their  courses,  espe- 
cially where  they  flow  through  a  region  of 
made  earth,  such  as  is  the  case  with  the  lower 
Mississippi  River,  and  in  other  great  rivers  of 
the  world.  The  loose  earth  is  continually 
shifted  by  the  current,  and  where  the  current 
is  not  very  strong  it  will  often  hold  the  water 
back  to  such  an  extent  of  accumulated  weight 
that  the  flood  will  break  over  at  some  weak 
point  on  its  banks  and  make  a  new  course  for 
itself. 

One  of  the  great  rivers  of  China — the 
Hwangho — often  causes  dire  destruction  to 
life  and  property  owing  to  change  in  its  bed 
from  time  to  time.  It  is  estimated  that  be- 
tween the  years  of  1851-66  this  river  caused 
the  loss  of  from  30,000,000  to  40,000,000  lives 
through  drowning  and  famine  by  the  destruc- 
tion of  crops. 

Floods  in  rivers  are  occasioned  from  vari- 
ous causes.  Of  course  the  primary  cause  is 
the  same  in  all  cases,  that  is,  from  precipita- 
tion of  moisture  in  the  form  of  rain  or  snow. 
Some  rivers  are  so  related  to  the  area  of  rain- 
fall and  to  the  permeability  of  the  soil  that 
there  is  but  little  variation  in  the  amount  of 
discharge  throughout  the  year.  The  great 


IRfvers  an&  fflooDs,  157 

river  of  South  America,  the  Amazon,  is  an  in- 
stance of  a  river  of  this  class.  A  certain 
number  of  the  smaller  rivers  that  feed  it  lie 
in  the  area  of  rainfall  during  the  whole  of  the 
year;  for  instance,  the  streams  of  the  upper 
Amazon  are  being1  fed  by  rains  at  one  season 
of  the  year,  when  those  feeding  the  river  lower 
down  are  at  the  lowest  stage.  When  the  rainy 
season  prevails  in  the  upper  section  of  the 
river  the  dry  season  prevails  farther  down, 
while  at  another  season  of  the  year  these  con- 
ditions are  reversed.  Therefore,  though  the 
Amazon  has  a  larger  drainage  basin  than  any 
other  river  in  the  world,  and  in  some  parts  the 
yearly  rainfall  is  280  inches,  there  is  no  very 
great  fluctuation  in  the  stages  of  water.  The 
Orinoco  River,  which  flows  through  Vene- 
zuela, and  whose  drainage  area  is  largely  cov- 
ered with  mountains,  has  a  greater  fluctuation 
than  any  other  river,  the  difference  between 
high  and  low  water  amounting  to  seventy  feet. 
The  River  Nile  has  an  annual  rise  of  from 
fourteen  to  twenty-six  feet.  This  river  is  the 
sole  dependence  of  the  inhabitants  of  lower 
Egypt,  and  their  sustenance  depends  upon  the 
height  to  which  the  river  rises;  if  it  does  not 
rise  high  enough  the  agricultural  lands  are 
not  sufficiently  irrigated,  and  if  it  rises  too 
high  their  crops  are  destroyed  by  the  floods. 
In  this  section  they  depend  entirely  upon  the 
overflow  of  the  Nile  for  irrigation,  and  not 


158  matured  Miracles, 

upon  the  rainfall.  There  is  scarcely  ever  a 
rainfall  in  lower  Egypt  except  about  once  a 
year  on  the  coast  of  the  Mediterranean. 
After  ascending  the  river  for  a  short  distance 
we  come  into  an  area  of  no  rain  for  a  distance 
of  1500  miles  along  the  river.  Egypt  has  a 
superficial  area  of  about  115,200  square  miles, 
and  only  about  one-twelfth  of  this  area  is  in  a 
position  to  be  cultivated. 

As  there  is  no  rainfall  in  this  region,  the 
sole  dependence  for  agricultural  purposes  is 
from  the  River  Nile  when  it  rises  to  a  suffi- 
cient height  to  admit  of  irrigation.  The  river 
brings  down  quantities  of  rich  earth  which 
during  the  overflow  is  deposited,  and  thus  the 
agricultural  regions  are  refertilized  annually. 

The  River  Nile  is  what  is  called  a  tropical 
river  and  is  fed  by  the  rains  in  upper  Egypt 
caused  by  the  monsoon  winds  that  prevail  in 
that  section  of  Africa  during  the  summer  sea- 
son, as  they  do  in  India.  As  has  been  ex- 
plained in  a  former  chapter,  the  monsoon 
winds  blow  steadily  for  about  six  months  from 
off  the  southern  ocean.  These  winds  are 
highly  charged  with  moisture,  which  is  not 
precipitated  till  it  strikes  the  mountainous 
regions  of  the  interior.  Here  the  high  moun- 
tains, which  are  often  snow-capped,  cause  a 
profuse  precipitation,  which  runs  off  into  the 
various  feeders  of  the  Nile,  causing  a  gradual 
rise  in  the  river  that  reaches  the  highest  point 


IRfvere  anD  ffloofcs,  159 

about  September  of  each  year.  If  the  Nile 
should  dry  up,  or  if  the  annual  floods  should 
materially  change  in  height,  it  would  make  a 
desert  region  of  all  that  portion  of  Egypt  now 
so  productive. 

The  great  rivers  of  China,  the  Yang-tse- 
Kiang  and  the  Hwangho,  are  also  tropical 
rivers  and  have  an  annual  flood.  Sometimes 
the  rise  is  as  much  as  fifty-six  feet.  These 
annual  floods  are  also  caused  by  the  monsoon 
winds  that  carry  moisture  from  the  ocean, 
which  is  condensed  and  precipitated  in  the 
mountains  of  central  Asia.  The  conditions 
are  substantially  the  same  as  those  which  pre- 
vail at  the  sources  of  the  Nile  in  Africa. 

Rivers  are  produced  from  all  sorts  of  causes, 
some  of  them  flowing  only  during  the  rainy 
season,  while  others  are  fed  by  melting  snow 
from  the  higher  mountains,  and  as  the  snow  is 
rarely  melted  away  entirely  during  the  sum- 
mer, in  the  high  mountains,  there  is  a  con- 
tinual flow  from  this  source.  The  snow  forms 
a  system  of  storage,  so  that  the  water  is  held 
back  and  is  gradually  given  up  as  it  melts.  If 
this  were  not  true  mountainous  regions  would 
be  subjected  to  disastrous  floods.  If  the  pre- 
cipitation were  always  in  the  form  of  rain  it 
would  immediately  run  off  instead  of  being 
distributed  over  a  whole  season.  The  Platte 
is  an  instance  of  a  river  largely  fed  by  the 
melting  snows — of  the  Rocky  Mountains. 


160  fftatute'0 

In  the  region  of  glaciers  in  the  mountains 
of  Alaska  and  Switzerland  rivers  are  fed  by 
the  melting  ice.  These  rivers  are  usually  of 
a  milky  color  occasioned  by  the  pulveriza- 
tion of  rock  caused  by  the  grinding  of  the 
great  glaciers  as  they  flow  down  the  gulches 
in  the  mountain  side.  In  some  regions  these 
glacial  rivers  have  a  diurnal  variation.  This 
is  caused  by  the  fact  that  the  glacier  is  so 
situated  that  it  freezes  at  night,  which  checks 
the  flow,  and  thaws  in  the  daytime,  which  in- 
creases it. 

Rivers  are  to  the  globe  what  the  veins  are 
to  the  animal  organization.  They  pick  up  the 
surplus  moisture  not  needed  in  the  growth  of 
vegetation  and  for  the  sustenance  of  animal 
life,  and  carry  it  on,  together  with  the  debris 
that  it  gathers  in  its  course,  to  the  great  reser- 
voirs, the  seas  and  oceans,  where  it  is  re- 
distilled and  purified  by  the  action  of  the  sun's 
rays.  From  here  it  is  carried  back  in  the 
form  of  invisible  moisture  and  again  precipi- 
tated in  the  purified  state,  to  help  carry  on  the 
great  operations  of  growth — animal  and  vege- 
table. The  vaporized  moisture  that  is  carried 
back  by  the  winds  and  redistributed  corre- 
sponds to  the  blood,  after  it  has  been  purified 
and  is  carried  back  through  the  arteries  to  the 
extremities  and  capillary  vessels  which  feed 
and  nourish  the  bodily  organs. 


CHAPTEK  XX. 

TIDES. 

Anyone  who  has  spent  a  summer  at  the  sea- 
shore has  observed  that  the  water  level  of  the 
ocean  changes  twice  in  about  twenty-four 
hours,  or  perhaps  it  would  be  a  better  state- 
ment to  say  that  it  is  continually  changing 
and  that  twice  in  twenty-four  hours  there  is  a 
point  when  it  reaches  its  highest  level  and  an- 
other when  it  reaches  its  lowest.  It  swings 
back  and  forth  like  a  pendulum,  making  a 
complete  oscillation  once  in  twelve  hours. 
When  we  come  to  study  this  phenomenon 
closely  we  find  that  it  varies  each  day,  and 
that  for  a  certain  period  of  time  the  water 
will  reach  a  higher  level  each  succeeding  day 
until  it  culminates  in  a  maximum  height, 
when  it  begins  to  gradually  diminish  from  day 
to  day  until  it  has  reached  a  minimum.  Here 
it  turns  and  goes  over  the  same  round  again. 
It  will  be  further  observed  that  the  time  occu- 
pied between  one  high  tide  and  the  next  one  is 
a  trifle  over  twelve  hours.  That  is  to  say,  the 
two  ebbs  and  flows  that  occur  each  day  require 

161 


162  feature's  /BMracles, 

a  little  more  than  twenty-four  hours,  so  that 
the  tidal  day  is  a  little  longer  than  the  solar 
day.  It  corresponds  to  what  we  call  the  lunar 
day. 

As  all  know,  the  moon  goes  through  all  its 
phases  once  in  twenty-eight  days.  The  tvie 
considered  in  its  simplest  aspect  is  a  struggle 
on  the  part  of  the  water  to  follow  the  moon. 
There  is  a  mutual  attraction  of  gravitation  be- 
tween the  earth  and  ohe  moon.  Because  the 
water  of  the  earth  is  mobile  it  tends  to  pile  up 
at  a  point  nearest  the  moon.  But  the  earth 
as  a  whole  also  moves  toward  the  moon,  and 
more  than  the  water  does,  keeping  its  round 
shape,  while  its  movable  water  (practically 
enveloping  it)  is  piled  up  before  it  toward  the 
moon  and  left  accumulated  behind  it  away 
from  the  moon.  So  that  in  a  rough  way  it  is 
a  solid  sound  earth,  surrounded  by  an  oval 
body  of  water :  the  long  axis  of  the  oval  repre- 
senting the  high  tides,  which,  as  they  follow 
the  moon,  slide  completely  around  the  earth 
once  in  every  twenty-four  hours.  Thus,  there 
are  really  two  high  tides  and  two  low  tides 
moving  around  the  earth  at  the  same  time; 
and  this  accounts  for  the  two  daily  tides. 

We  have  accounted  for  the  time  when  they 
occur  in  the  fact  that  the  water  attempts  to 
follow  the  moon,  but  this  does  not  account  for 
the  gradual  changes  in  the  amount  of  fluctua- 
tion from  day  to  day.  The  problem  is  com- 


plicated  by  the  fact  that  the  sun  also  has  an 
attraction  for  the  earth  as  well  as  the  moon. 
But  from  the  fact  that  the  sun  is  something 
like  400  times  further  from  the  earth  than  the 
moon  is,  and  also  the  fact  that  the  attraction 
of  one  body  for  another  varies  inversely  as  the 
square  of  the  distance,  the  moon  has  an  im- 
mense advantage  over  the  sun,  although  so 
much  smaller.  If  the  power  of  the  moon  were 
entirely  suspended,  or  if  the  moon  were  blotted 
out  of  existence,  there  would  still  be  a  tide. 
The  fluctuation  between  high  and  low  tide 
would  not  be  nearly  so  great  as  it  is  at  pres- 
ent, but  it  would  occur  at  the  same  time  each 
day,  because  it  would  be  wholly  a  product  of 
the  sun. 

It  will  be  easily  seen  that  these  two  forces 
acting  upon  the  water  at  the  same  time  will 
cause  a  complicated  condition  in  the  move- 
ment of  the  waters  of  the  ocean.  There  will 
come  a  time  once  in  twenty-eight  days  when 
tLe  sun  and  the  moon  will  act  conjointly,  and 
both  will  pull  in  the  same  direction  at  the 
same  time  upon  the  water.  This  joint  action 
of  the  sun  and  moon  produces  the  highest  tide, 
which  is  called  the  "  spring  "  tide.  From  this 
point,  however,  the  tides  will  grow  less  each 
day,  because  the  relation  of  the  sun  and  moon 
is  constantly  changing,  owing  to  the  fact  that 
it  requires  365  days  for  the  sun  to  complete 
his  apparent  revolution  around  the  earth, 


164  matured  jfllMracles. 

while  the  moon  does  her  actual  course  in 
twenty-eight  days.  When  the  sun  and  moon 
have  changed  their  relative  positions  so  that 
they  are  at  right  angles  to  each  other  with 
reference  to  the  earth — at  a  quarter-circle 
apart — the  sun  and  moon  will  be  pulling 
against  each  other;  at  least  this  is  the  point 
where  the  moon  is  at  the  greatest  disadvantage 
with  reference  to  its  ability  to  attract  the 
water. 

Because  one-quarter  around  the  earth  the 
sun  is  creating  his  own  tide,  which  to  that  ex- 
tent counteracts  the  effect  produced  by  the 
moon,  the  tide  under  the  moon  at  this  point  is 
at  its  lowest  point  and  is  called  the  "  neap  " 
tide.  When  the  moon  has  passed  on  around 
the  earth  to  a  point  where  it  is  opposite  to 
that  of  the  sun — at  a  half -circle  apart — there 
will  be  another  spring  tide,  and  then  another 
neap  tide  when  it  is  on  the  last  quarter,  and 
from  that  point  the  tide  will  increase  daily 
until  it  reaches  the  point  where  the  sun  and 
moon  are  in  exact  line  with  reference  to  the 
earth's  center,  when  another  spring  tide 
occurs.  From  this  it  will  be  seen  that  there 
are  two  spring  tides  and  two  neap  tides  in  each 
twenty-eight  days.  This  is  the  fundamental 
law  governing  tides. 

There  are  many  other  conditions  that 
modify  tidal  effects.  Neither  the  sun  nor  the 
moon  is  always  at  the  same  distance  from  the 


165 


earth.  So  that  there  will  be  a  variation  at 
times  in  high  and  low  tides.  For  instance,  it 
will  happen  sometimes  that  when  both  the  sun 
and  moon  are  acting  conjointly  they  will  both 
be  at  their  nearest  point  to  the  earth,  and 
when  this  is  the  case  the  spring  tide  will  be 
much  higher  than  usual. 

For  many  years  the  writer  has  observed  that 
artesian  wells,  made  by  deep  borings  of  small 
diameter  into  the  earth  to  a  water  supply,  have 
a  daily  period  of  ebb  and  flow,  as  well  as  a 
neap  and  spring  tide,  the  same  as  the  tides  of 
the  ocean,  except  that  the  process  is  reversed. 
The  time  of  greatest  flow  of  an  artesian  well 
will  occur  at  low  tide  in  the  ocean.  This 
might  be  ^accounted  for  from  the  fact  that 
when  the  tide  is  at  its  height  the  moon  is  also 
pulling  upon  the  crust  of  the  earth,  which 
would  tend  to  take  the  pressure  off  the  sand 
rock  which  lies  one  or  two  thousand  feet  be- 
low the  surface  and  through  which  the  flow  of 
water  comes,  and  thus  slacken  the  flow. 
When  the  moon  is  in  position  for  low  tide,  the 
crust  of  the  earth  would  settle  back  and  thus 
produce  a  greater  pressure  upon  the  water- 
bearing rock.  This  is  the  only  theory  that  has 
suggested  itself  to  the  writer  that  would  seem 
to  account  for  these  phenomena. 

Looked  at  from  one  standpoint,  it  is  easy  to 
account  for  tidal  action.  But  when  we  at- 
tempt to  make  up  a  table  giving  the  hour  and 


166  filature's  Miracles. 

minute  as  well  as  the  height  of  the  tide  at  that 
particular  time  we  find  that  we  have  a  very 
complicated  mathematical  problem.  How- 
ever, tahles  are  made  out  so  that  we  know  at 
just  what  time  in  the  day  a  tide  will  occur 
every  day  in  the  year. 


CHAPTEK  XXI. 

WHAT    IS    A    SPONGE? 

Before  entering  upon  the  great  subject  of 
water  and  ice — two  of  the  most  tremendous 
factors  in  world-building — let  us  consider  a 
small  matter,  so  far  as  its  permanent  effects 
are  concerned,  yet  one  which  enters  largely 
into  the  comfort  and  health  of  mankind,  and 
which,  though  an  animal,  may  be  discussed 
where  it  belongs — under  "Water." 

There  are  few  things  more  familiar  about 
the  ordinary  household  than  a  piece  of  sponge, 
and  yet,  perhaps,  there  are  but  few  things 
about  which  there  is  so  little  known.  The 
sponge  had  been  in  use  many,  many  years  be- 
fore it  was  given  a  place  in  either  the  animal 
or  vegetable  kingdom.  The  casual  observer, 
because  he  saw  it  attached  to  a  rock,  jumped 
to  the  conclusion  that  it  was  of  vegetable 
origin.  But  after  being  kicked  back  and 
forth,  so  to  speak,  from  one  kingdom  to  the 
other,  even  by  what  are  called  well-educated 
people,  it  has  finally  been  received  into  the 
family  of  animals;  a  dignity  in  which  the 
sponge  itself  seems  to  take  but  little  interest. 

167 


168  matured  /Ifcfracles* 

The  sponge  is  found  in  the  bottom  of  the 
sea;  at  no  very  great  depth,  however.  It  is 
usually  attached  to  a  rock  or  some  other  sub- 
stance and  it  is  due  to  this  fact  chiefly  that  it 
has  been  classed  as  a  vegetable.  At  least  one 
scientist  has  attempted  to  give  it  a  place  be- 
tween the  two  kingdoms,  but  this  only  adds 
confusion  without  giving  any  satisfactory  ex- 
planation of  its  origin.  It  seems  to  belong 
to  a  very  low  order  of  animal  life.  It  breathes 
water  instead  of  air,  but  probably,  like  many 
other  water  animals,  it  absorbs  the  oxygen 
from  the  air  which  is  more  or  less  contained 
in  the  water.  There  is  a  process  of  oxidation 
going  on  within  the  sponge  in  a  manner  some- 
what as  we  find  it  in  ordinary  animal  life, 
and  like  the  animal  it  expels  carbon  dioxide. 
All  this,  however,  is  carried  on  apparently 
without  any  lungs  or  any  digestive  organs,  or 
in  fact  any  of  the  organs  that  are  common  to 
the  animals  of  the  higher  order.  The  sponge, 
however,  as  we  see  it  in  our  bathrooms,  is  only 
the  framework,  bony  structure,  or  skeleton  of 
the  animal. 

The  sponge  is  exceedingly  porous  and 
readily  absorbs  water  or  any  fluid  by  the  well- 
known  process  of  capillary  attraction.  The 
sponge  fiber  is  very  tough  and  is  not  like  any- 
thing known  to  exist  in  the  vegetable  king- 
dom. The  substance  analyzes  almost  the  same 
as  ordinary  silk,  which  all  know  is  an  animal 


TKHbat  16  a  Sponge?  169 

product.  If  we  burn  a  piece  of  sponge  it  ex- 
hibits very  much  the  same  phenomena  as  the 
burning  of  hair  or  wool,  and  the  smell  is  very 
much  the  same. 

The  structure  of  a  piece  of  sponge  when 
examined  under  a  microscope  is  a  wonderfully 
complicated  fabric.  Under  the  microscope  it 
shows  a  network  of  interlacing  filaments  run- 
ning in  every  direction  in  a  system  of  curved 
lines  intersecting  and  interlacing  with  each 
other  in  a  manner  to  leave  capillary  openings. 

It  is  a  wonderful  structure,  and  one  that  a 
mechanical  engineer  could  get  many  valuable 
lessons  from.  It  will  stand  a  strain  in  one 
direction  as  well  as  another.  There  are  no 
special  laminations  or  lines  of  cleavage;  it  is 
very  resilient  or  elastic,  and  readily  yields  to 
pressure,  but  as  readily  comes  back  to  its  nor- 
mal position  when  the  pressure  Is  relieved.  If 
we  examine  the  body  of  a  sponge  we  shall 
notice  that  there  are  occasional  large  openings 
into  it,  but  everywhere  surrounded  by  smaller 
ones.  If  we  should  capture  a  live  sponge  and 
place  it  in  an  aquarium  with  sea  water,  where 
we  could  study  it,  we  should  find  a  circulation 
constantly  going  on,  and  that  water  was  con- 
stantly sucked  in  at  the  smaller  openings  all 
over  the  outside  of  the  sponge  and  as  continu- 
ously ejected  from  the  large  openings.  This 
process  constitutes  what  corresponds  in  the 
higher  order  of  animals  to  both  respiration 


i?o  matured  flStracles. 

and  blood  circulation,  combined.  The  sponge 
feeds  upon  substances  that  are  gathered  up 
from  the  sea  water,  and  breathes  the  air  con- 
tained in  the  same,  so  that  it  breathes,  eats, 
and  drinks  through  the  same  set  of  organs. 

When  we  first  capture  a  live  sponge  from 
the  sea  it  has  a  slimy,  dirty  appearance,  and  is 
very  heavy.  The  sponge  is  found  to  be  filled 
with  a  glutinous  substance  that  is  the  fleshy 
part  of  the  animal.  It  is  very  soft  and  jelly- 
like,  and  after  the  sponge  is  dead  it  is  readily 
squeezed  out,  by  a  process  which  is  called 
"taking  the  milk  out,"  which  leaves  simply 
the  skeleton,  the  only  useful  part  as  an  article 
of  commerce.  This  fleshy  substance,  in  life, 
has  somewhat  the  appearance  and  composi- 
tion of  the  white  of  an  egg. 

The  mechanical  process  by  which  the  sponge 
takes  its  nourishment  is  exceedingly  interest- 
ing. There  are  small  globe-shaped  cells  with 
openings  through  them  that  are  lined  with 
little  hairlike  projections  that  move  in  such  a 
manner  as  to  suck  the  water  in  at  one  side  of 
the  cell  and  push  it  out  at  the  other.  These 
little  fibers  are  technically  called  "  cilia."  We 
might  describe  them  as  little  suction  pumps 
that  are  located  at  many  points  in  the  sponge, 
all  acting  conjointly  to  produce  a  circulation 
through  the  finer  openings  or  capillary  vessels 
and  finally  discharging  into  the  larger  cham- 
bers which  carry  off  the  residue.  If  we  should 


TKHbat  fa  a  Sponge?  1V1 

analyze  the  water  as  it  is  sucked  into  the 
sponge  and  that  which  issues  from  it  through 
the  larger  openings,  we  should  find  a  differ- 
ence between  the  two.  The  expelled  water 
would  contain  more  or  less  carbon  dioxide. 

There  are  many  different  varieties  of 
sponge,  and,  while  they  all  possess  certain 
characteristics  in  common,  they  are  still  very 
different  in  many  respects.  Some  of  them  are 
large  and  coarse,  while  others  are  exceedingly 
soft  and  velvety.  What  is  called  a  single 
sponge  is  a  colony  of  animals  rather  than  a 
single  animal;  at  least  they  are  so  regarded 
by  zoologists.  This  can  hardly  be  true  if  we 
regard  the  sponge  itself  as  a  part  of  the  ani- 
mal. If  the  sponge  is  simply  regarded  as  the 
house  in  which  the  animal  lives  then  it  be- 
comes a  great  tenement  with  numerous  occu- 
pants. But  it  is  a  tenement  upon  which  the 
life  of  the  sponge  depends,  and  is  a  part  of  it. 

The  sponge  could  not  breathe  without  the 
fibrous  structure  in  the  cells  containing  the 
machinery  for  producing  the  circulation.  It 
will  be  seen  that  the  sponge,  while  it  is  an  ani- 
mal, is  of  the  very  simplest  variety,  so  far  as 
its  organs  are  concerned.  True,  its  frame- 
work is  very  complicated,  but  the  organs  for 
sustaining  the  life  of  the  animal  are  the  sim- 
plest possible.  The  little  self-acting  pumps 
pull  the  water  into  the  sponge  through  the 
smaller  openings,  where  it  appropriates  the 


i?2  matured 

food  substance  from  the  water  and  where  a 
chemical  action  takes  place  which  builds  up 
the  fleshy  substance  of  the  animal,  and  then 
expels  the  residue  which  is  not  needed  to  sup- 
port its  life. 

Simple  as  it  is,  however,  as  a  mechanical 
structure,  the  life  and  growth  of  the  sponge  is 
as  mysterious  as  that  of  the  most  highly 
organized  animal  or  even  the  soul  of  man. 
We  can  study  out  the  structure  of  a  plant  or 
animal;  we  can  analyze  it  and  tell  what  are 
the  elements  of  which  it  is  composed;  we  can 
describe  the  mechanical  operations  that  are 
carried  on  and  the  chemical  combinations  that 
take  place,  but  no  man  has  ever  yet  solved  the 
mystery  of  life,  even  in  the  lowest  form — 
whether  animal  or  vegetable. 

The  sponge,  whether  considered  as  a  single 
or  compound  animal,  has  the  power  to  repro- 
duce itself,  and  here  the  mystery  of  life  is  as 
much  hidden  as  it  is  in  God's  highest  creation. 
It  has  been  stated  that  every  sponge  contains 
a  large  number  of  separate  cells  which  carry 
on  the  operation  of  circulation  and  respira- 
tion, and  may  be  likened  to  the  heart  and 
lungs  of  an  animal  of  a  higher  creation.  Zo- 
ologists claim  that  each  one  of  these  cells 
represents  a  separate  animal,  living  in  a  com- 
mon structure.  However  this  may  be,  it  is  an 
interesting  fact  that  the  sponge  has  the  power 
of  secreting  ova  that  grow  in  large  numbers 


TObat  10  a  Sponge?  173 

in  little  sacks  until  they  have  reached  a  cer- 
tain stage  of  progress,  when  they  are  expelled 
from  the  mother  sponge  and  turned  adrift  in 
the  great  ocean  to  struggle  for  their  own  exist- 
ence. These  eggs  do  not  differ  much  in  their 
structure  and  composition  from  an  ordinary 
hen's  egg,  except  that  there  is  no  shell,  only  a 
skin  provided  with  little  fibers  called  cilia, 
that  project  from  it,  and  by  the  movement  of 
these  the  embryo  sponge  is  able  to  propel  itself 
through  the  water.  It  thus  lives  until  it  has 
reached  a  certain  stage  of  development,  when 
it  seeks  out  a  pebble  or  rock,  to  which  it  at- 
taches itself  at  one  end — preparation  for 
which  has  been  made  by  its  peculiar  structure 
during  its  life  when  it  was  free  to  float  around 
through  the  water.  It  is  now  a  prisoner  and 
chained  to  the  rock  it  has  selected  for  the 
foundation  of  its  home.  Having  no  longer 
any  use  for  the  little  cilia,  which  enabled  it 
to  swim  through  the  water,  it  now  loses  them. 
Here  is  a  beautiful  illustration  of  how  nature 
provides  for  the  necessities  of  the  smallest 
things,  and  how  when  the  necessity  that  de- 
manded a  certain  condition  passes  by  the  con- 
dition passes  with  it.  The  embryo  begins  to 
show  a  fibrous  development,  which  is  the  be- 
ginning of  the  framework  of  a  new  sponge. 
Evolution  goes  on,  every  step  of  which  is  as 
mysterious  as  a  miracle,  until  the  growing 
thing  is  a  full-grown  sponge,  equipped  with 


174  iftature's 

the  means  for  respiration,  circulation,  feeding, 
digestion,  and  reproduction. 

Sponges  grow  in  the  bottom  of  the  sea  at 
different  depths.  They  are  obtained  by  divers 
who  make  a  business  of  gathering  them.  The 
best  sponges  are  called  the  Turkish  sponge, 
which  are  very  soft  and  velvety,  and  may  be 
bleached  until  they  are  nearly  white  by  sub- 
jecting them  to  the  action  of  certain  acids. 
The  divers  become  very  expert,  but  they  do 
not  have  the  modern  equipments  of  a  diving 
suit.  The  Syrian  divers  in  the  Mediterranean 
go  down  naked  with  a  rope  attached  to  their 
waists  and  a  stone  attached  to  the  rope  to 
cause  them  to  sink,  together  with  a  bag  for 
carrying  the  sponges.  They  have  trained 
themselves  until  they  can  remain  under  water 
from  a  minute  to  a  minute  and  a  half,  and  in 
that  time  can  gather  from  one  to  three  dozen 
sponges.  The  ordinary  depth  to  which  they 
descend  is  from  eight  to  twelve  fathoms.  But 
a  very  expert  diver  will  go  down  as  far  as  forty 
fathoms.  The  better  class  of  sponges  are  said 
to  grow  in  the  deeper  waters.  The  coarse  in- 
ferior sponges  are  called  the  Bahama  sponge. 
This  sponge  is  of  a  peculiar  shape,  growing 
more  like  a  brush,  with  long  bristly  fiber. 

The  trade  in  sponges  is  quite  large.  The 
consumption  in  Great  Britain  alone  amounts 
to  about  $1,000,000  per  annum. 

The  sponge  as  an  animal  possesses  many  ad- 


10  a  Sponge?  if 5 

vantages  over  his  more  aristocratic  neighbor, 
man.  He  breathes  but  he  has  no  lungs,  and 
therefore  cannot  have  pneumonia.  He  di- 
gests his  food,  but  he  has  no  stomach,  and 
therefore  never  has  dyspepsia,  gastritis,  or  any 
of  the  many  ailments  that  belong  to  that  much 
abused  organ.  He  has  no  intestines,  and 
therefore  cannot  have  appendicitis  or  Asiatic 
cholera  or  any  of  the  long  train  of  diseases  in- 
cident to  those  complicated  organs.  He  has 
no  nervous  system — oh,  happy  sponge! — there- 
fore he  cannot  have  nervous  prostration,  hys- 
teria, or  epilepsy.  He  has  no  use  for  doctors, 
and  therefore  has  no  unpleasant  discussions 
with  his  neighbors  about  the  relative  merits  of 
the  different  schools  of  medicine.  If  he  has 
any  predilections  in  the  way  of  "  pathies  "  we 
should  say  that  he  is  a  hydropath.  While  he 
is  a  great  drinker,  he  is  not  at  all  convivial — 
he  drinks  only  water,  and  takes  that  in  soli- 
tary silence.  He  sows  all  his  wild  oats 
when  he  is  very  young,  while  he  has  the 
freedom  to  roam  at  will.  He  soon  tires  of 
this,  however,  for  he  selects  the  rock  that  is 
to  be  the  foundation  of  his  future  home  and 
there  settles  down  for  life,  "  wrapt  in  the  soli- 
tude of  his  own  originality."  He  is  not 
troubled  with  wars  or  rumors  of  wars.  His 
eyes  are  never  startled  or  his  nerves  shaken 
by  the  scare  headlines  of  yellow  journalism. 
The  one  sensation  of  his  life,  if  sensation  he 


176  IRature's  Afracle*, 

ever  has,  is  when  a  great  ugly  creature  of  some 
Oriental  clime  comes  down  to  his  home  and 
tears  him  away  from  his  native  rock,  carries 
him  to  the  surface,  and  there  literally 
"squeezes  the  life  out  of  him."  He  finally 
dies  of  the  "grip,"  and  here  he  sinks  to  the 
level  of  his  more  aristocratic  neighbor. 

But  there  is  another  side  to  our  philosophy. 
If  the  sponge  is  exempt  from  all  these  ills  that 
we  have  enumerated  it  is  because  he  is  in- 
capable of  suffering  and  is  therefore  incapable 
of  enjoyment.  Those  beings  that  have  the 
ability  to  suffer  most  have  also  the  ability  to 
enjoy  most.  The  higher  the  type  of  civiliza- 
tion the  greater  possibilities  it  offers  for  real 
enjoyment — also  for  real  misery.  This  being 
true,  it  should  be  the  aim  of  highly  civilized 
people  to  eliminate  as  far  as  possible  those 
things  that  make  for  misery,  and  cultivate 
those  things  that  make  for  happiness  in  the 
highest  and  best  sense. 


CHAPTER  XXII. 

WATER    AND    ICE. 

We  now  have  entered  upon  a  subject  that 
is  of  intense  interest,  studied  from  the  stand- 
point of  facts  as  they  exist  to-day  and  of  his- 
tory as  we  read  it  in  the  rocks  and  bowlders 
that  we  find  distributed  over  the  face  of  the 
earth. 

The  whole  northern  part  of  the  United 
States  extending  to  a  point  south  of  Cin- 
cinnati was  at  one  time  covered  with  a  great 
ice-sheet,  traces  of  which  are  plainly  visible 
to  anyone  who  has  made  anything  of  a  study 
of  this  subject.  The  glaciers  now  to  be  seen 
in  British  Columbia  and  Alaska,  great  as  they 
seem  to  one  viewing  them  to-day,  are  by  com- 
parison with  what  once  existed  simply  micro- 
scopic specks  of  ice.  Glaciers,  like  rivers,  flow 
by  gravity,  following  the  lowest  bed  and  lines 
of  least  resistance;  the  difference  being  that 
in  the  one  case  the  flow  is  rapid,  while  in  the 
other  it  is  scarcely  visible,  except  by  measure- 
ment from  day  to  day.  Before  entering  upon 
a  description  of  the  law  that  governs  the  flow 
of  glaciers,  let  us  stop  and  give  a  little 
m 


Ifa  fRature'0  /HMracles. 

study  to  the  phenomena  of  water  as  exhibited x 
when  it  is  at  the  freezing  point.  Water  is 
such  a  large  factor  in  the  make-up  of  our 
globe  and  the  air  that  surrounds  it  that  it  be- 
comes a  very  interesting  and  important  study 
to  anyone  who  wishes  to  understand  the  phe- 
nomena of  nature  that  are  closely  related  to 
it. 

As  all  know,  pure  water  is  a  compound  of 
two  gases,  oxygen  and  hydrogen,  combined  in 
the  proportion  of  two  atoms  of  hydrogen  and 
one  of  oxygen. 

Let  us  now  study  this  fluid  in  its  relation  to 
heat.  The  reader  is  referred  to  the  chapters 
on  heat  in  Vol.  II.,  where  it  is  stated  that  heat 
is  a  mode  of  motion.  It  is  also  stated  that 
heat  is  a  form  of  energy,  and  that  energy  is 
indestructible,  that  an  unvarying  amount  of 
it  exists  in  some  form  or  another  throughout 
the  universe.  It  is  not  always  manifested  as 
heat  or  electricity,  although  both  of  these  are 
always  in  evidence  as  active  agents  of  force. 
Much  of  the  energy  is  simply  stored — all  the 
time  possessing  the  ability  to  do  work  or  to  be 
converted  into  any  of  its  known  forms,  such  as 
heat,  light,  electricity,  or  mechanical  motion. 
A  weight  that  is  wound  up  has  required  a  cer- 
tain amount  of  energy  to  elevate  it  to  the 
position  that  it  occupies.  While  in  its  ele- 
vated position  it  possesses  energy,  although 
not  active.  Energy  in  this  form  is  called  po- 


Mater  an&  1fce,  WQ 

tential  (possible)  energy,  and  has  the  power  to 
do  work  if  released.  Active  energy  is  called 
kinetic  (moving)  energy,  and  the  sum  of  these 
two  energies  is  a  constant  quantity. 

We  will  now  study  energy  as  it  is  related  to 
water  in  the  form  of  heat.  There  is  a  kind 
of  heat  called  "  latent  heat,"  which  is  not  heat 
at  all,  but  stored  energy,  waiting  to  be  turned 
into  heat,  or  light,  or  some  other  active  form. 
Properly  speaking,  heat  is  a  movement  of  the 
atoms  of  matter,  the  intensity  of  which  is 
measurable  in  degrees,  and  called  its  tempera- 
ture. To  use  the  term  latent  heat  as  meaning 
concealed  heat,  which  must  reappear  as  heat, 
is  a  misnomer  and  is  very  misleading.  If  it 
is  proper  to  call  a  wound-up  spring  or  weight 
latent  heat  then  its  present  use  is  a  correct 
one.  What  was  formerly  termed  latent  heat 
is  simply  a  form  of  potential  energy.  When 
sensible  heat  that  is  measurable,  as  tempera- 
ture, disappears  in  the  performance  of  some 
sort  of  work,  especially  in  connection  with  cer- 
tain phenomena  relating  to  water,  we  call  it — 
or  rather  miscall  it — latent  heat:  but  the 
phrase  would  better  be  "  stored  energy." 

The  action  of  water  under  heat  is  very 
peculiar,  and  in  order  to  get  a  correct  under- 
standing of  the  phenomena  exhibited  in 
glacial  action  we  also  need  to  understand  the 
phenomena  of  water  at  the  freezing  point. 
As  is  well  known,  fresh  water  freezes  at  32  de- 


180  mature'* 

grees  Farhenheit,  and  at  the  moment  of  freez- 
ing there  is  a  sudden  expansion  to  such  an  ex- 
tent that  a  cubic  foot  of  ice  will  occupy  a 
much  larger  space  than  it  will  in  the  form  of 
water;  and  because  it  occupies  so  much  larger 
space  it  is  lighter  than  the  same  bulk  of  water 
would  be,  and  therefore  it  floats  in  water. 

At  the  point  of  freezing,  the  thermometer  if 
placed  on  the  ice  will  register  32  degrees.  If 
the  ice  is  allowed  to  melt,  the  water  at  the  mo- 
ment of  liquefaction  would  be  found  to  regis- 
ter the  same  degree  of  temperature  as  the  ice 
when  first  frozen.  And  yet  there  has  been  a 
vast  expenditure  of  energy  between  the  points 
of  liquefaction  and  congelation,  notwithstand- 
ing the  temperature  of  ice  may  be  lowered, 
after  it  is  formed,  many  degrees,  which  is 
measurable  by  the  thermometer.  Suppose  we 
take  a  piece  of  ice  which  is  10  degrees  below 
the  freezing  point  and  insert  in  it  a  thermom- 
eter. If  now  we  apply  heat  to  this  ice  the  ther- 
mometer will  gradually  rise  until  it  reaches  the 
melting  point  at  32  degrees  Fahrenheit,  where 
it  will  stand  until  all  the  ice  is  melted.  The 
application  of  heat  is  going  on  steadily,  but 
there  are  no  indications  of  movement  in  the 
mercury  until  the  last  trace  of  ice  with  which 
it  is  in  contact  has  been  liquefied.  After  the 
ice  is  all  melted,  if  the  application  of  heat  to 
the  body  of  liquefied  ice  be  continued,  the 
column  of  mercury  will  resume  its  movement 


Mater  an&  1fce,  181 

upward  until  it  reaches  the  boiling  point, 
where  it  is  again  arrested.  And  no  matter 
how  much  heat  is  applied  to  the  boiling  water, 
if  in  an  open  vessel,  the  thermometer  remains 
the  same  until  all  the  water  is  evaporated. 
Here  are  two  curious  facts,  and  they  are  facts 
that,  if  we  can  master  them,  will  serve  as  a 
key  to  the  understanding  of  much  that  is  mys- 
terious in  nature. 

It  will  be  our  endeavor  to  give  the  reader  a 
mental  picture  of  what  is  taking  place  during 
the  time  the  ice  is  melting  and  the  thermom- 
eter is  stationary.  Do  not  suppose  that  you 
can  understand  this,  even  so  far  as  it  is  under- 
standable, by  a  casual  reading  without 
thought.  No  man  was  ever  yet  able  to  present 
a  picture  to  the  mind  of  another,  however 
clearly  and  simply  it  may  be  done,  unless  that 
other  mind  is  receptive.  When  a  photog- 
rapher trains  his  camera  upon  an  object,  how- 
ever intense  the  light  may  be  and  however 
clean-cut  the  picture  that  is  thrown  upon  the 
plate  in  the  camera,  unless  that  plate  is  prop- 
erly sensitized  so  that  the  picture  may  be  im- 
pressed upon  it,  all  of  the  other  conditions  are 
in  vain.  The  reader  is  always  a  part  of  the 
book  he  is  reading. 


CHAPTEK  XXIII. 

STORED    ENERGY    IN    WATER. 

In  our  last  chapter  we  traced  the  upward 
movement  in  the  mercury  of  the  thermometer 
from  10  degrees  below  the  freezing  point  up  to 
the  boiling  point  of  water.  We  found  that  the 
thermometer  was  arrested  at  32  degrees  and 
remained  stationary  at  that  point  until  all  the 
ice  was  melted,  notwithstanding  the  fact  that 
heat  was  being  constantly  applied.  After  the 
ice  is  all  melted  the  mercury  moves  upward 
until  it  reaches  the  boiling  point  of  water, 
where  the  movement  is  again  arrested,  and  al- 
though the  heat  is  being  continuously  applied, 
it  remains  stationary  until  all  the  water  is 
evaporated.  If  we  push  the  process  still  fur- 
ther, with  a  sufficient -application  of  energy  we 
can  separate  the  vapor  molecules  into  their 
original  elements,  oxygen  and  hydrogen. 

Let  us  go  back  now  to  the  freezing  point  of 
water  and  see  what  is  becoming  of  the  heat 
that  is  consumed  in  melting  the  cake  of  ice, 
and  still  does  not  produce  any  effect  upon  the 
mercury  in  the  thermometer.  Sensible  heat, 

183 


Stores  3£ner0g  in  Water*          183 

as  before  stated,  is  a  movement  of  the  atoms 
of  matter,  and  temperature,  as  it  affects  the 
thermometer,  is  a  measure  of  the  intensity  of 
motion  exhibited  by  these  atoms. 

In  the  experiment  of  the  block  of  ice  that  in 
the  beginning  is  10  degrees  below  the  freezing 
point,  as  shown  by  the  thermometer,  the  mole- 
cules have  a  definite  intensity  of  motion.  The 
intensity  of  this  motion  increases  when  heat 
is  applied  until  it  reaches  32  degrees,  when  it 
remains  stationary  until  all  of  the  ice  is 
melted.  At  this  point  there  is  a  rearrange- 
ment of  the  molecules  of  water  as  it  assumes 
the  liquid  state.  To  perform  this  rearrange- 
ment requires  a  certain  amount  of  work  done, 
which  is  analogous  to  the  winding  up  of  a 
weight  to  a  certain  distance.  There  has  been 
energy  used  in  winding  up  the  weight,  but 
that  energy  now  is  not  destroyed,  nor  still  in 
the  form  of  heat,  but  is  in  the  potential  state — 
ready  to  do  some  other  kind  of  work.  So,  the 
heat  that  has  been  applied  to  the  melting  ice 
has  been  utilized  during  the  process  of  its 
liquefaction  in  rearranging  the  water 
molecules  and  putting  them  in  a  state  of 
strain,  so  to  speak,  like  the  weight  that  is 
wound  up  to  a  certain  height.  There  is  a  cer- 
tain amount  of  potential  energy  that  is  stored 
in  the  molecules  of  water  that  will  be  given  up 
and  become  active  energy  in  the  form  of  heat, 
if  the  water  is  again  frozen.  To  melt  a  cubic 


184  matured  /HMraclea, 

foot  of  ice  requires  as  much  heat  as  it  would 
to  raise  a  cubic  foot  of  water  144  degrees  Fah- 
renheit. But,  as  we  have  seen,  while  all  of 
this  energy  is  absorbed  as  heat,  it  is  not  lost  as 
energy.  It  ceases  to  be  kinetic  or  active  and 
becomes  potential  energy.  This  (let  us  re- 
peat) has  been  called  latent  heat.  The  term 
grew  out  of  the  old  idea  that  heat  was  a  fluid 
and  that  when  it  became  latent  it  hid  itself 
away  somewhere  in  the  interatomic  spaces  of 
matter  and  ceased  to  be  longer  sensible  heat. 
It  came  into  existence  in  the  same  manner  and 
occupies  the  same  place  in  the  science  of  heat 
that  the  word  "  current "  does  in  the  science  of 
electricity:  both  of  them  are  misnomers. 

When  the  ice  is  all  melted  potential  energy 
is  no  longer  stored,  but  is  manifested  in  the 
sensible  heating  of  water,  the  degree  of  which 
is  measurable  by  the  thermometer,  until  it 
reaches  the  boiling  point,  where  it  is  again  ar- 
rested. All  of  the  surplus  heat  above  that 
temperature  is  consumed  in  rending  the  liquid 
water  into  moisture  globules  that  float  away 
into  the  air,  each  one  of  them  charged  with  a 
store  of  potential  energy.  Let  us  follow  this 
vapor  spherule  as  it  floats  into  the  upper 
regions  of  the  atmosphere.  Myriads  of  its 
fellows  travel  with  it  until  it  reaches  a  point 
where  condensation  takes  place,  when  it  col- 
lapses and  unites  with  other  vapor  particles  to 
form  water  again.  In  doing  this  the  heat  that 


Stored  J&mtQV  in  Mater*          185 


was  expended  upon  it  to  disengage  it  (whether 
the  heat  was  artificial  or  that  of  the  sun's 
rays)  now  reappears  either  as  sensible  heat  or 
as  electricity,  or  both.  And  this  is  what  is 
meant  in  meteorology  by  latent  heat  becom- 
ing sensible  heat  at  the  time  of  condensation  ; 
in  fact,  it  is  stored  or  "  potential  "  energy  be- 
coming active  or  kinetic,  and  assumes  the 
form  of  heat  or  electricity,  as  before  stated. 
We  have  thus  reviewed  the  matter  of  the  fore- 
going chapter  in  order  to  follow  the  course  of 
the  stored  energy  from  the  melting  of  the  ice 
to  the  vapor,  and  back  again  to  water:  to 
doubly  impress  the  fact  that  the  energy  used 
was  not  consumed,  but  still  exists  and  is 
ready  for  further  work. 

During  the  progress  of  a  hailstorm,  it  has 
been  stated,  one  of  the  factors  that  is  active  to 
produce  this  phenomenon  is  the  intense  ascen- 
sional force  that  is  given  to  the  moisture-laden 
air,  caused  by  intense  heat  at  the  surface  of 
the  earth.  This  condition  forces  the  moisture 
vapor  to  higher  regions  of  the  atmosphere  than 
is  the  case  with  the  ordinary  thunderstorm. 
Another  factor  that  is  undoubtedly  active  in 
producing  hail  under  these  circumstances  is 
that  when  condensation  takes  place  in  the 
higher  regions,  and  is  therefore  more  energetic 
on  account  of  the  intenser  cold,  the  potential 
energy  that  is  set  free  by  the  moisture 
spherules  takes,  in  a  larger  degree,  the  form 


186  Wature'0 


of  electricity  rather  than  heat,  as  is  the  case 
under  more  ordinary  circumstances.  While 
in  the  end  this  electrical  energy  becomes 
active  heat,  it  does  not  for  the  time  being,  and 
thus  favors  the  ready  congelation  of  the  con- 
densed moisture  into  hailstones.  Hailstorms 
are  always  attended  by  incessant  thunder  and 
lightning,  and  this  fact  favors  the  theory  ad- 
vanced above. 

It  will  be  easily  seen  from  a  study  of  the 
foregoing  what  a  wonderful  factor  evaporation 
(which  is  a  product  of  the  sun's  rays)  is,  in 
the  play  of  celestial  dynamics.  It  ascends 
from  the  surface  of  the  earth  or  ocean  laden 
with  a  stored  energy,  the  power  of  which  no 
man  can  compute,  and  beside  which  gravita- 
tion is  a  mere  point.  In  the  upper  regions  of 
atmosphere  this  potential  force  under  certain 
conditions  is  released  and  becomes  an  active 
factor,  not  only  in  the  formation  of  cloud  and 
the  precipitation  of  rain,  hail,  and  snow,  but 
it  disturbs  the  equilibrium  of  the  air  and  sets 
that  in  motion. 

Certain  physicists  deny  that  evaporation  has 
anything  to  do  with  atmospheric  electricity. 
They  tell  us  that  it  is  caused  by  the  arrest  of 
the  energy  of  the  sunbeam  by  the  clouds  and 
vapor  in  the  upper  atmosphere.  We  admit 
that  a  part  of  the  energy  is  so  arrested,  and  is 
stored,  for  the  time,  in  moisture  globules  by  a 
process  of  cloud  evaporation  to  transparent 


Stored  ;6ner0B  in  Mater.          187 

vapor  again.  Yet  this  does  not  hinder  the 
same  process  from  going  on  at  the  surface  of 
the  earth  wherever  there  is  water  or  moisture. 
But  they  tell  us  that  the  electroscope  does  not 
show  any  signs  of  electrification  in  the  evap- 
orated moisture.  Of  course  it  does  not.  The 
electroscope  is  not  made  to  detect  the  presence 
of  energy  except  when  set  free  as  electricity. 

A  wound-up  spring  does  not  seem  to  be  elec- 
trified, but  if  it  is  released  the  energy  stored  in 
it  will  be  transformed  into  electricity  if  the 
conditions  are  right.  Just  so,  the  energy  re- 
quired to  put  the  moisture  spherule  into  a 
state  of  strain  is  latent  until  some  power  re- 
leases it,  when  it  reappears  as  active  energy  of 
some  form. 

We  have  now  followed  the  relation  of  heat 
to  water  from  a  point  10  degrees  below  freez- 
ing up  to  where  it  was  forced  into  its  original 
gases,  oxygen  and  hydrogen.  These  gases 
have  stored  in  them  a  wonderful  amount  of 
potential  energy.  When  one  pound  of  hydro- 
gen and  eight  pounds  of  oxygen  unite  to  form 
water  the  mechanical  value  of  the  energy 
given  up  at  that  time  in  the  form  of  heat  is 
represented  by  47,000,000  pounds  raised  to  one 
foot  in  height.  And  this  is  the  measure  of  the 
energy  that  was  put  into  nine  pounds  of  water 
to  force  it  from  a  state  of  vapor  into  its  con- 
stituent gases.  After  the  combination  of  the 
gases  into  a  state  of  vapor  the  temperature 


188  nature's  jflJMracles, 

sinks  to  that  of  boiling  water.  The  amount 
of  energy  given  up  in  condensing  the  nine 
pounds  of  vapor  into  nine  pounds  of  water  is 
equal  to  6,720,000  foot-pounds.  If  this  nine 
pounds  of  water  is  now  cooled  from  the  boiling 
point  to  32  degrees  Fahrenheit  we  come  to  the 
final  fall,  where  the  potential  energy  that  is 
stored  in  the  operation  of  melting  ice  is  given 
up  suddenly  at  the  moment  of  freezing,  which 
in  nine  pounds  of  water  is  993,546  foot  pounds. 
Professor  Tyndall,  in  speaking  of  the 
amount  of  energy  that  is  given  up  between  the 
points  where  the  constituent  gases  unite  to 
form  nine  pounds  of  water  and  the  point 
where  it  congeals  as  ice,  says :  "  Our  nine 
pounds  of  water,  at  its  origin  and  during  its 
progress,  falls  down  three  precipices — the  first 
fall  is  equivalent  in  energy  to  the  descent  of  a 
ton  weight  down  a  precipice  22,320  feet  high — 
over  four  miles;  the  second  fall  is  equal  to 
that  of  a  ton  down  a  precipice  2900  feet  high, 
and  the  third  is  equal  to  a  fall  of  a  ton  down  a 
precipice  433  feet  high.  I  have  seen  the  wild 
stone  avalanches  of  the  Alps,  which  smoke  and 
thunder  down  the  declivities  with  a  vehemence 
almost  sufficient  to  stun  the  observer.  I  have 
also  seen  snowflakes  descending  so  softly  as 
not  to  hurt  the  fragile  spangles  of  which  they 
are  composed.  Yet  to  produce  from  aqueous 
vapor  a  quantity  which  a  child  could  carry  of 
that  tender  material  demands  an  exertion  of 


Stores  J&netQv  in  Mater.          189 


energy  competent  to  gather  up  the  shattered 
blocks  of  the  largest  stone  avalanche  I  have 
ever  seen  and  pitch  them  to  twice  the  height 
from  which  they  fell." 

When  we  contemplate  the  foregoing  facts  as 
related  to  so  small  an  amount  of  water  as  nine 
pounds,  and  multiply  this  result  by  the 
amount  of  snow-  and  rain-fall  each  year  and 
the  amount  of  ice  that  is  congealed  and  again 
liquefied  by  the  power  of  the  sun's  rays,  we  are 
appalled,  and  shrink  from  the  task  of  attempt- 
ing to  reduce  the  amount  of  energy  expended 
in  a  single  year  to  measurable  units. 

Having  considered  water  in  its  relation  to 
heat  in  the  preceding  chapters,  we  will  now 
take  up  the  subject  of  water  in  its  relation  to 
ice  and  snowfall  and  the  phenomena  exhibited 
in  ice  rivers,  commonly  called  glaciers. 

When  water  is  under  pressure  the  freezing 
point  is  reduced  several  degrees  below  32 
degrees  Fahrenheit.  This  fact  has  been  de- 
termined by  confining  water  in  a  close  vessel 
and  putting  it  under  pressure  and  subject- 
ing it  to  a  freezing  mixture,  and  by  this 
means  determining  the  freezing  point  under 
such  conditions.  By  putting  a  bullet  or 
something  of  that  nature  into  the  water 
that  is  subjected  to  pressure  one  can  tell 
by  shaking  it  when  the  freezing  point  is 
reached.  If  water  is  put  under  pressure  and 
cooled  to  a  point  below  32  degrees,  and  yet  still 


190  matured  dfcfracles. 

remains  in  the  liquid  state,  it  may  be  suddenly 
congealed  by  taking  off  the  pressure;  this 
shows  that  the  pressure  helps  to  hold  the  mole- 
cules in  the  position  necessary  for  the  liquid 
state,  and  prevents  the  rearrangement  of  them 
that  takes  place  at  the  moment  of  freezing. 
When  the  water  molecules  are  arranged  for 
the  liquid  condition  they  may  be  compared  to 
a  spring  that  is  wound  up  and  held  in  position 
by  the  heat  energy  that  is  stored  in  the  water. 
And  when  this  energy  is  given  up  to  a  certain 
degree  the  power  that  holds  the  spring  wound 
up  is  suddenly  released,  when  it  unwinds  and 
occupies  a  larger  space.  There  is  a  force  that 
we  may  call  polar  force,  which  is  constantly 
tending  to  push  the  molecules  of  water  into  an 
arrangement  such  as  we  see  when  crystalliza- 
tion takes  place — as  it  always  does  in  the  act 
of  freezing.  These  polar  forces  cannot  act  so 
long  as  the  energy  in  the  form  of  heat  is  suffi- 
cient to  hold  the  water  in  the  fluid  state.  But 
the  moment  this  energy,  which  tends  to  hold 
it  in  the  fluid  state,  falls  below  that  which 
tends  to  rearrange  it  into  the  crystalline  form, 
it  is  overcome  by  the  superior  power  of  the 
latter  force,  and  we  have  the  phenomenon  of 
solidified  water. 

A  very  interesting  experiment  may  be  per- 
formed with  a  block  of  ice  by  anyone  when  the 
ice  is  near  the  melting  point.  If  a  wire  is  put 
around  the  ice  and  a  sufficient  weight  is  sus- 


Stores  I6ner0£  in  Water.         1^1 

pended  to  it,  the  pressure  of  the  wire  on  the 
ice  will  gradually  liquefy  that  portion  imme- 
diately under  the  wire,  which  allows  it  to  sink 
into  the  ice  slowly,  and  as  this  process  goes  on 
the  ice  freezes  together  again  behind  the  wire, 
so  that  in  time  the  wire  will  pass  entirely 
through  the  block  and  leave  it  still  a  solid 
block,  as  it  was  before  the  experiment  began. 

This  is  an  interesting  fact  which  it  will  be 
well  to  remember  when  we  come  to  explain 
glacial  action,  or  rather  the  law  that  governs 
glacial  action.  If  we  take  two  pieces  of  melt- 
ing ice  and  bring  them  together  they  imme- 
diately congeal  at  the  point  of  contact.  This 
phenomenon  is  called  "  regelation."  Ice  has 
some  of  the  properties  of  a  viscous  substance. 
It  will  yield  slowly  to  pressure,  especially  when 
near  the  melting  point,  but  if  put  under  a  ten- 
sional  strain  it  will  break,  as  any  brittle  sub- 
stance will,  so  that  it  has  the  properties  of 
both  viscosity  and  brittleness.  Ordinarily  we 
are  in  the  habit  of  treating  water  as  a  fluid 
and  ice  as  a  solid,  but  from  what  has  gone  be- 
fore the  reader  must  understand  that  in  a  cer- 
tain sense  ice  should  be  treated  as  having 
semi-fluidic  properties. 


CHAPTER  XXIV. 

WHY    DOES    ICE    FLOAT? 

Nature  is  full  of  surprises.  By  a  long 
series  of  experimental  investigations  you 
think  you  have  established  a  law  that  is  as  un- 
alterable as  those  of  the  Medes  and  Persians. 
But  once  in  a  while  you  stumble  upon  phe- 
nomena that  seem  to  contradict  all  that  has 
gone  before. 

These,  however,  may  be  only  the  exceptions 
that  prove  the  rule.  It  is  recognized  as  a  fun- 
damental law  that  heat  expands  and  cold  con- 
tracts; that  the  atom  when  in  a  state  of  in- 
tense motion  (which  is  the  condition  produc- 
ing the  effect  that  we  call  "heat")  requires 
more  room  than  when  its  motions  are  of  a  less 
amplitude.  In  other  words,  an  increase  in  the 
amplitude  of  atomic  motion  is  heating,  while 
a  decrease  is  cooling.  It  follows  from  the 
above  statement  that  the  colder  a  body  be- 
comes the  smaller  will  be  its  dimensions. 
There  are  two  or  three,  and  perhaps  more,  ex- 
ceptions to  this  rule,  and  the  most  notable  one 
is  that  of  water.  Water  follows  the  same  law 
that  all  other  substances  do  under  the  action 


Does  1fce  Afloat?  193 

of  heat  and  cold,  within  certain  limits  only. 
If  we  take  water,  say,  at  50  degrees  Fahren- 
heit and  subject  it  to  cold  it  will  gradually 
contract  in  bulk  until  it  reaches  39  degrees 
Fahrenheit.  At  this  point,  very  curiously, 
contraction  ceases,  and  here  we  find  the  maxi- 
mum density  of  water.  If  the  temperature  is 
still  lowered  we  find  the  bulk  is  gradually  in- 
creasing instead  of  diminishing  (as  is  the  rule 
with  other  fluids),  and  when  it  reaches  the 
freezing  point  there  is  a  sudden  and  marked 
expansion,  so  much  so  that  a  cubic  foot  of  ice, 
which  is  solidified  water,  will  not  weigh  as 
much  as  a  cubic  foot  of  water  before  it  freezes 
— hence  it  floats. 

Let  us  try  an  experiment.  Take  a  small 
glass  flask,  terminating  in  a  long  neck,  say  of 
four  to  six  inches,  and  of  small  diameter. 
Suppose  the  water  in  the  glass  to  be  at  50  de- 
grees Fahrenheit.  Fill  the  flask  with  water 
until  it  stands  halfway  up  the  neck  at  50  de- 
grees temperature.  Now  immerse  the  flask 
gradually  in  hot  water,  and  observe  the 
effect.  For  a  moment  the  water  will  lower  in 
the  neck  of  che  tube,  but  this  is  due  to  the 
fact  that  the  glass  expands  before  the  heat  is 
communicated  to  the  water  and  enlarges  its 
capacity.  But  immediately  the  water  will  be- 
gin to  rise  as  the  heat  is  communicated  to  it, 
and  will  continue  to  expand  up  to  the  boiling 
point.  Now  take  the  flask  out  of  the  hot 


104  lftature'0  /HMraclea. 

water  and  gradually  introduce  it  into  a  freez- 
ing mixture  made  of  broken  ice  and  salt. 
Immediately  the  water  will  begin  to  fall  in 
the  tube,  showing  that  it  is  contracting  under 
the  cold,  and  it  will  continue  to  contract  until 
it  reaches  a  temperature  of  39  degrees  Fah- 
renheit, when  it  will  come  to  a  standstill  and 
then  proceed  to  expand  as  the  temperature  of 
the  water  lowers.  When  it  reaches  the  freez- 
ing point  the  fluid  can  no  longer  rise  in  the 
neck  of  the  flask,  which  is  broken  by  the  sud- 
den expansion  that  takes  place  at  this  point. 

To  show  what  an  irresistible  power  resides 
in  the  atoms  of  which  the  body  is  made,  let  us 
take  an  iron  flask  with  walls  one-half  inch  or 
more  in  thickness;  fill  it  with  water  and  seal 
it  up  by  screwing  on  the  neck  an  iron  cap ;  now 
plunge  it  into  the  freezing  mixture,  and  the 
first  effect  will  be  to  contract  the  water  unless 
it  is  already  below  39  degrees  Fahrenheit,  but 
when  it  reaches  that  point  expansion  sets  in, 
which  continues  to  the  freezing  point,  when  a 
greatly  increased  expansion  takes  place  sud- 
denly. The  walls  of  the  iron  flask,  although 
a  half-inch  in  thickness,  are  no  longer  able  to 
resist  the  combined  efforts  of  the  billions  upon 
billions  of  the  atoms  of  which  the  water  is 
made  up,  in  their  individual  clamor  for  more 
room,  hence  the  flask  is  shivered  into  pieces. 

There  are  one  or  two  other  substances  which 
are  exceptions  to  the  general  rule,  but  we  will 


2>oes  1fcc  Afloat?  195 

mention  only  one,  which  is  the  metal  bismuth. 
If  we  should  melt  a  sufficient  amount  to  fill  an 
iron  flask,  such  as  we  have  described,  and  sub- 
ject it  to  the  same  freezing  process,  the  flask 
will  be  broken  the  same  as  in  the  experiment 
made  with  the  water. 

A  query  arises,  Why  this  phenomenon? 
Why  does  water  follow  a  different  law  in 
cooling  from  that  of  nearly  all  other  sub- 
stances ? 

This  is  a  case  where  it  is  much  easier  to  ask 
a  question  than  to  answer  it.  When  water 
solidifies  at  the  moment  of  freezing,  crystalli- 
zation sets  in.  But  what  is  crystallization? 
Crystallization  is  a  peculiar  arrangement  of 
the  molecules  of  matter,  which  takes  place  in 
some  substances  when  they  pass  from  the 
liquid  to  the  solid  form.  The  molecules  as- 
sume definite  forms  and  shapes,  according  to 
the  nature  of  the  substance.  When  water 
assumes  the  solid  form  under  the  action  of 
cold  the  molecules  arrange  themselves  accord- 
ing to  certain  definite  and  fixed  laws,  the  re- 
sult of  which  is  to  increase  the  bulk  to  a  con- 
siderable extent  over  that  which  the  same 
number  of  molecules  would  occupy  at  a  tem- 
perature of  39  degrees  Fahrenheit.  Hence, 
as  has  been  heretofore  stated,  a  given  block  of 
solidified  water  is  lighter  than  the  same  bulk 
would  be  in  the  fluid  state,  and  this  is  the  rea- 
son why  ice  floats. 


196  ttature'0  /DMracle0. 

What  would  happen  in  case  nature  did  not 
make  this  exception  to  the  laws  of  expansion 
and  contraction  by  heat  and  cold,  in  the  case 
of  water?  First,  our  lakes  would  freeze  from 
the  bottom  upward ;  as  soon  as  the  surface  be- 
came frozen,  or  even  colder  than  the  water 
underneath,  it  would  drop  to  the  bottom,  the 
warmer  water  below  coming  up  by  a  well- 
known  law — that  the  warmer  fluid  rises  and 
the  colder  falls.  This  circulation  would  con- 
tinue until  ice  began  to  form,  which  would  im- 
mediately drop  to  the  bottom,  and  this  process 
would  go  on  until  the  whole  mass  were  frozen 
solid.  In  the  same  way  our  rivers  in  the 
northern  climates  would  freeze  from  the  bot- 
tom, and  in  time  our  valleys  would  fill  up  with 
ice  to  a  thickness  that  the  summer's  sun  would 
never  melt,  and  gradually  all  north  of  a  cer- 
tain zone  would  become  a  great  glacier,  ren- 
dering not  only  the  lakes  and  rivers  but  also 
the  surface  of  the  earth  unfitted  for  animal 
life. 

Those  who  believe  that  the  laws  of  nature 
are  the  creations  of  a  beneficent  and  all-wise 
Intelligence  will  see  in  this  exception  to  the 
general  law  in  the  case  of  freezing  water  a 
striking  evidence  of  design.  But  those  who 
have  no  such  belief  will  say  it  is  a  most  for- 
tunate though  fortuitous  circumstance  (a  say- 
ing they  will  have  to  make,  regarding  thou- 
sands of  other  things  in  nature),  and  go  on 


Boca  1fce  float?  197 

floundering   in   the   interminable   sea   of   "  I 
don't  know." 

The  atom  when  it  is  acting  under  the  direc- 
tion of  a  fixed  law  is  a  giant  in  strength.  And 
when  its  individual  strength  is  multiplied  by 
billions  upon  billions  the  combined  energy 
exerted  produces  a  power  that  is  irresistible. 
Not  only  has  nature  endowed  these  atoms  with 
this  wonderful  power,  but  she  has  also  willed 
that  they  arrange  themselves  in  lines  of 
beauty.  In  confirmation  of  this  we  need  only 
to  study  the  work  of  the  frost  upon  our  win- 
dow panes.  As  we  lie  in  our  beds  on  a  cold 
night  and  exhale  moisture  from  our  lungs 
it  settles  upon  the  window  panes  of  our 
bedrooms,  where  Nature — that  wonderful 
artist — forms  it  into  beautiful  pictures  th&t 
gladden  our  eyes  when  we  awake : 

Most  beautiful  things  ;  there  are  flowers  and  trees, 
And  bevies  of  birds,  and  swarms  of  bees, 
And  cities,  and  temples,  and  towers,  and  these 
All  pictured  in  silver  sheen. 


CHAPTEE  XXV. 

GLACIERS. 

Glaciers  are  rivers  of  ice,  and,  like  other 
rivers,  some  of  them  are  small  and  some  very 
large.  They  flow  down  the  gorges  from  high 
mountains,  whose  peaks  are  always  covered 
with  a  blanket  of  eternal  snow.  Summer  and 
winter  the  snow  is  precipitated  upon  these 
mountains,  and  from  time  to  time  the  heat  of 
the  sun's  rays  softens  the  snow,  when  by  its 
great  weight  it  packs  more  closely  together 
until  it  is,  in  many  cases,  formed  into  solid 
ice-cakes.  If  we  take  a  quantity  of  snow  or  a 
quantity  of  granulated  ice  and  put  it  under  a 
sufficient  pressure  we  can  produce  clear  solid 
ice,  and  it  is  by  this  process  that  ice  is  formed 
out  of  the  snow  and  hail  that  falls  continually 
upon  the  tops  of  these  glacial  mountains.  We 
have  seen  that  ice  possesses  certain  viscous  or 
semi-fluidic  properties  and  that  it  will  yield  to 
pressure,  but  if  we  put  it  under  sufficient  ten- 
sional  strain  it  snaps  like  glass  or  any  other 
brittle  substance.  As  the  snows  upon  these 
mountains  pile  up  higher  and  higher  the  pres- 
sure becomes  greater  and  greater  until  it 
reaches  a  point  where  the  mass  begins  to  move 

198 


Glaciers,  190 

gradually  down  the  mountain  side,  following 
the  gulches  and  defiles  that  furnish  a  path  of 
least  resistance  to  its  flow. 

At  the  sides  and  bottom,  where  there  is  con- 
tact with  the  earth,  the  movement  is  slower 
than  it  is  at  the  surface  and  in  the  middle  of 
the  ice  stream.  If  there  were  no  curves  in 
the  ravine  or  gulch  through  which  it  flows  the 
point  of  greatest  movement  would  be  confined 
to  the  middle  of  its  width.  But  in  flowing 
through  a  winding  gulch  the  most  rapid  flow 
follow  the  lines  of  greatest  pressure,  and  this 
line  is  deflected  from  side  to  side,  so  that  the 
line  of  greatest  flow  is  more  winding  than  is 
the  bottom  of  the  valley  through  which  it 
flows.  (The  movement  is  called  a  "  flow,"  but 
it  is  very  sluggish,  only  a  few  inches  in  a  day, 
as  will  appear  later.) 

If  the  bottom  and  sides  of  the  valley  were 
straight  the  surface  of  the  ice  would  be  com- 
paratively even;  I  say  comparatively,  for  as 
compared  with  a  smooth  surface  it  would  be 
very  rough;  but  there  would  be  none  of  the 
great  crevasses  or  openings  now  to  be  found  in 
the  ice,  which  sometimes  are  very  large  and 
extend  to  a  great  depth.  If  in  its  downward 
course  the  bottom  of  the  ravine  suddenly  be- 
comes steeper,  the  top  of  the  ice  is  put  under 
a  tensional  strain  which  causes  it  to  break, 
thus  forming  the  crevasses. 

If  at  the  bottom  of  the  descent  the  valley 


200  mature'*  Miracles, 

curves  upward  or  preserves  the  straight  line 
for  a  considerable  distance,  these  crevasses  will 
close  at  the  top  and  perhaps  open  at  the  bot- 
tom, and  the  blocks  of  ice  will  freeze  together 
to  such  an  extent  that  the  water  caused  by  the 
melting  ice  will  flow  on  top  until  it  comes  to 
another  crevasse,  where  it  runs  through  to  the 
bottom  or  underflow,  which  is  always  an  at- 
tendant of  a  glacier. 

The  glacier  continues  its  flow  down  the 
mountain  side  till  in  some  cases  it  reaches 
quite  to  the  valley  below,  and  in  others  it  stops 
short,  as  the  action  of  the  sun  is  so  great  that 
it  melts  entirely  away  at  this  point  as  fast  as 
it  moves  down.  In  the  winter  time,  however, 
the  glacier  may  flow  far  down  into  the  valley 
and  will  accumulate  greatly  in  bulk,  owing  to 
the  fact  that  the  ice  forms  from  the  precipita- 
tion of  snow  on  top  faster  than  it  melts  away 
underneath.  If  it  were  not  for  the  fact  that 
in  summer  the  glaciers  melt  faster  than  they 
form,  the  whole  valley  would  in  time  become  a 
great  river  of  ice.  It  is  the  case  in  Switzer- 
land that  some  years  the  accumulation  is 
greater  from  snowfall  than  diminution  from 
melting.  If  this  condition  should  continue 
it  would  become  a  serious  matter. 

In  the  downward  flow  of  a  glacier — slow  as 
it  is — there  is  an  exhibition  of  wonderful 
power ;  great  bowlders  are  torn  from  their  beds 
and  either  ground  to  powder  or  carried  down 


Glaciers.  201 

to  the  end  of  the  glacier,  to  be  dropped  with 
the  other  debris  that  has  been  carried  there  by 
the  same  force,  forming  an  accumulation  that 
geologists  call  the  "moraine."  Of  these  mo- 
raines we  will  speak  more  fully  later  on. 

It  was  the  privilege  of  the  writer  some  years 
since  to  visit  the  great  glaciers  of  Switzerland 
and  to  some  extent  study  their  action.  Some 
rivers  have  their  origin  chiefly  in  melting 
glaciers.  They  start  as  ice  rivers  and  end  in 
rivers  of  water.  The  effects  during  the  great 
ice  age  of  some  of  these  glacial  rivers,  which 
are  now  extinct,  are  very  remarkable;  we  shall 
have  occasion  to  refer  to  them  when  we  come 
to  treat  of  the  glacial  period. 

There  is  a  glacial  river  flowing  which  is  fed 
largely  by  the  great  Rhone  glacier  in  Switzer- 
land. The  water  from  this  river  is  almost  as 
white  as  milk,  which  is  occasioned  by  the 
grinding  action  of  the  great  ice  blocks  on  the 
rock  as  it  flows  down  the  sides  of  the  moun- 
tain. These  glacial  rivers  are  much  higher  in 
summer,  of  course,  than  in  winter,  some  of 
them  having  not  only  an  annual  fluctuation, 
but  a  diurnal  one.  The  former  is  caused  by 
the  cold  of  winter,  and  the  latter  because  it- 
freezes  to  some  extent  at  night  and  checks  the 
flow  of  water.  The  difference  between  day  and 
night  in  these  high  altitudes  is  very  marked. 
While  it  is  extremely  hot  in  the  sun,  it  is  cool 
the  moment  we  step  into  the  shade. 


202  nature's 

I  remember  walking*  across  one  of  the  gla- 
ciers in  the  Alps,  called  the  Mer  de  Glace,  one 
clear  day  in  summer,  when  I  suffered  so  much 
from  the  heat,  although  standing  upon  a  sea 
of  ice,  that  it  was  necessary  to  carry  an 
umbrella.  In  fact,  during  my  stay  there  was  a 
case  of  sunstroke  that  occurred  upon  this  same 
glacier.  This  intense  heat  during  the  day 
melts  the  surface  of  the  ice,  which  forms 
streams  that  run  along  on  the  top  of  a  glacier 
until  they  come  to  a  crevasse  or  riffle  in  the 
ice  river,  where  they  plunge  down  and  become 
a  part  of  the  glacial  stream  that  is  flowing 
underneath  the  ice. 

The  speed  at  which  these  ice  streams  flow 
varies  greatly  with  the  size  of  the  glacier  as  to 
width  and  depth  and  the  steepness  of  the 
grade,  and  many  other  conditions.  In  its 
movement  the  glacier  is  constantly  bending 
and  freezing  and  being  torn  asunder  by  ten- 
sional  strain,  yielding  and  liquefying  at  other 
points  by  pressure,  only  to  freeze  again  when 
that  pressure  is  removed.  This,  taken  in  con- 
nection with  the  friction  of  the  great  ice 
bowlders,  produces  a  movement  that  is  exceed- 
ingly complicated  in  its  actions  and  inter- 
actions. 

According  to  Professor  TyndalFs  investiga- 
tions, the  most  rapid  movement  observed  in 
the  glaciers  of  Switzerland  is  thirty-seven 
inches  per  day  at  the  point  of  greatest  move- 


Glaciers,  203 

ment.  From  this  point  each  way  the  motion 
gradually  diminishes  until  it  reaches  the  sides 
of  the  glacier,  where  the  motion  is  not  more 
than  two  or  three  inches. 

The  great  North  American  glaciers  move  at 
a  much  higher  rat©  of  speed.  We  are  in- 
debted to  Dr.  G.  Frederick  Wright,  author  of 
"  The  Ice  Age  in  North  America,"  who  spent 
a  month  studying  the  Muir  glacier  in  Alaska, 
for  many  details  concerning  that  great  ice 
river.  This  glacier  empties  into  Muir  Inlet, 
which  is  an  offshoot  of  Glacier  Bay.  It  is  situ- 
ated in  latitude  58  degrees  50  minutes  and 
longitude  136  degrees  40  minutes  west  of 
Greenwich.  The  bay  into  which  this  glacier 
empties  is  about  thirty  miles  long  and  from 
eight  to  twelve  miles  wide.  This  bay,  with 
its  great  glacier,  has  a  setting  of  grand  moun- 
tain peaks.  I  cannot  do  better  than  to  quote 
the  words  of  Dr.  Wright  when  he  describes  the 
location  of  this  glacier.  Dr.  Wright  lived  for 
a  month  in  a  tent  on  the  edge  of  this  bay,  a 
short  distance  below  the  face  of  the  great 
glacier,  where  the  icebergs  fell  off  every  few 
minutes  into  the  deep  water. 

He  says :  "  To  the  south  the  calm  surface  of 
the  bay  opened  outward  into  Cross  Sound 
twenty-five  miles  away.  The  islands  dotting 
the  smooth  surface  of  the  waters  below  us 
seemed  but  specks,  and  the  grand  vista  of 
snowclad  mountains  guarding  either  side  of 


204  lflature'0  Afraclee* 

Chatham  Strait  seemed  gradually  to  come  to 
a  point  on  the  southern  horizon.  Westward 
toward  the  Pacific  was  the  marvelous  outline 
of  the  southern  portion  of  the  St.  Elias  Alps. 
The  lofty  peaks  of  Crillon,  15,900  feet  high, 
and  Fair  Weather,  15,500  feet  high,  about 
twenty-five  miles  away  and  about  the  same  dis- 
tance apart,  stood  as  sentinels  over  the  lesser 
peaks." 

The  Muir  glacier  might  be  likened  to  a 
great  inland  sea  of  ice  fed  by  many  tribu- 
taries or  ice  rivers.  It  narrows  up  at  the  point 
where  it  empties  into  Muir  Inlet  to  10,664 
feet,  or  a  little  over  two  miles.  An  enormous 
pressure  is  exerted  at  this  point,  which  causes 
the  ice  to  flow  in  the  central  portion  at  the 
rate  of  about  seventy  feet  per  day.  There  is 
a  continual  booming,  like  the  firing  of  a  can- 
non, going  on,  caused  by  the  bursting  of  some 
great  iceberg  either  before  it  takes  its  final 
leap  into  the  water  or  at  the  moment  of  its 
fall.  At  the  point  where  these  great  icebergs 
drop  off  into  the  water  they  stand  like  a  solid 
wall  300  feet  above  its  surface.  Dr.  Wright 
says:  "From  this  point  there  is  a  constant  suc- 
cession of  falls  of  ice  into  the  water,  accom- 
panied by  loud  reports.  Scarcely  ten  minutes, 
either  night  or  day,  passed  during  the  whole 
month  without  our  being  startled  with  such 
reports ;  and  frequently  they  were  like  thunder 
claps  or  the  booming  of  cannon  at  the  bom- 


(Blacfers.  205 

bardment  of  a  besieged  city,  and  this  though 
our  camp  was  two  and  one-half  miles  below 
the  ice  front.  .  .  Repeatedly  I  have  seen  vast 
columns  of  ice  extending  up  to  the  full  height 
of  the  front  topple  over  and  fall  into  the 
water.  How  far  these  columns  extended  be- 
low the  water  could  not  be  told  accurately,  but 
I  have  seen  bergs  floating  away  which  were 
certainly  500  feet  in  length." 

It  is  estimated  that  the  cubical  contents  of 
some  of  these  icebergs  are  equal  to  40,000,000 
feet.  This  great  glacier  is  fed  by  the  con- 
stant precipitation  of  snow  upon  the  sides  and 
peaks  of  the  high  mountains  that  surround  its 
vast  amphitheater,  which  is  floored  with  ice- 
bergs. Wonderful  as  this  seems  to  us  to-day, 
it  is  scarcely  a  microscopic  speck  of  what  ex- 
isted during  the  ice  age -all  over  the  northern 
part  of  North  America. 

There  are  many  other  great  glaciers  in  the 
mountains  of  the  Pacific  coast.  Some  years 
ago  I  saw«one  of  these  immense  glaciers  in 
Britis'  Columbia,  from  a  point  called  Glacier 
Station,  in  the  Selkirk  Mountains,  on  the  Ca- 
nadian Pacific  Railroad.  It  was  during  the 
month  of  August,  when  all  of  the  region  was 
pervaded  by  a  dense  smoke  occasioned  by 
burning  forests.  This  glacier  is  a  very  showy 
one,  owing  to  the  steepness  of  the  side  of  the 
mountain  and  its  great  breadth.  All  the 
glaciers  that  exist  to-day  are  gradually  reced- 


206  matured 

ing,  and  are  destined  eventually  to  entirely 
disappear,  unless  there  is  a  change  in  meteoro- 
logical conditions,  which  some  scientists  claim 
will  be  the  case  if  we  only  wait  long  enough, 
when  again  all  this  northern  country  will  be 
covered  with  a  great  ice  sheet.  There  is  no 
doubt  in  regard  to  the  facts  concerning  a 
glacial  period  that  must  have  existed  in  the 
ages  past.  To  anyone  who  has  made  a  study 
of  the  subject  there  is  not  wanting  abundant 
evidence  to  prove  that  this  northern  country 
was  at  one  time  enveloped  with  a  great  ice 
sheet  of  enormous  thickness.  The  conditions 
that  existed  to  bring  about  such  a  state  of 
things  have  been  the  subject  of  much  specula- 
tion by  philosophers,  but  no  one,  as  yet,  has 
arrived  at  any  very  satisfactory  conclusion. 
Many  theories  have  been  advanced,  some  of 
them  not  worth  considering,  while  others  have 
many  things  that  give  them  a  show  of  plausi- 
bility. But  all  of  them  have  what  is  said  of 
the  Darwinian  theory,  "  a  missing  link."  It 
will  be  interesting,  however,  and  also  instruct- 
ive, to  know  what  can  be  said  in  favor  of  a  set 
of  conditions  that  would  produce  such  momen- 
tous results. 


CHAPTEK  XXVI. 

EVIDENCES   AND    THEORIES    OF    AN  ICE   AGE. 

There  is  abundant  and  unassailable  evidence 
that  at  one  time,  ages  ago,  a  vast  ice  sheet  cov- 
ered the  whole  of  the  northern  part  of  North 
America,  extending  south  in  Illinois  to  a  point 
between  latitudes  37  and  38.  This  is  the  most 
southerly  point  to  which  the  ice  sheet  reached. 
From  this  point  the  line  of  extreme  flow  runs 
off  in  a  northeasterly  and  northwesterly  direc- 
tion. The  northeasterly  line  is  through  south- 
eastern Ohio  and  Pennsylvania,  striking  the 
Atlantic  Ocean  about  at  New  York,  thence 
through  Long  Island  and  up  the  coast  of 
Massachusetts.  Northwesterly  it  follows  the 
Mississippi  River  to  its  junction  with  the  Mis- 
souri, which  it  crosses  at  a  point  some  miles 
west  of  this  junction,  following  the  general 
course  of  this  river  a  little  south  of  it  through 
the  States  of  Missouri,  Nebraska,  Dakota,  and 
Montana.  The  lines,  especially  the  northeast- 
erly one,  are  very  irregular,  shooting  out  into 
curves  and  then  receding.  This  line  of  ex- 
treme ice  flow  is  marked  by  glacial  drift  so 
prominently  that  no  one  who  has  studied  gla- 
cial action  can  doubt  for  a  moment  what  was 

207 


208  matured 

the  cause  of  these  deposits.  The  line  is  called 
the  "  terminal  moraine."  By  examining  a 
map  of  North  America  and  tracing  the  line  of 
the  moraine  as  we  have  described  it,  it  will  be 
seen  that  about  two-thirds  of  North  America 
was  at  one  time  covered  with  ice  to  a  greater 
or  less  depth.  How  deep,  is  simply  a  matter 
of  conjecture,  but  in  the  central  portions  of 
the  great  glacier,  where  was  the  bulk  of  snow- 
fall, it  must  have  reached  a  depth  of  several 
miles  to  account  for  the  enormous  pressure 
that  would  be  required  to  carry  the  ice  so  far 
southward. 

But  let  us  go  back  and  define  what  is  meant 
by  a  moraine.  A  moraine  is  a  name  given  to 
the  deposits  that  are  of  stone,  gravel,  and 
earth  that  have  been  carried  along  by  the 
movement  of  the  glaciers  and  deposited  at 
their  margins,  sometimes  piled  up  to  great 
depths.  The  composition  of  these  moraines  is 
determined  of  course  by  the  nature  of  the 
country  over  which  the  stream  of  ice  is  flow- 
ing. Bowlders  of  enormous  size  have  been 
carried  for  hundreds  of  miles,  and  the  experi- 
enced geologist  is  able  to  examine  any  one  of 
them  and  tell  us  where  its  home  was  before  the 
glacial  period.  Moraines  are  divided  into  dif- 
ferent classes  according  to  their  position  and 
constitution.  The  moraine  found  at  the  ex- 
treme limit  of  ice-flow  is  called  the  "terminal" 
moraine,  as  before  mentioned.  Those  that  are 


of  an  1fce 

found  inside  of  this  line  and  between  two  flows 
are  called  "medial"  moraines.  There  is  a 
subdivision  called  "  kettle  "  or  "  gravel "  mo- 
raines, which  are  very  prominent  in  northern 
Illinois  and  southern  Wisconsin,  and  may  be 
said  to  culminate  in  the  vicinity  of  Madison. 
This  moraine  is  a  great  deposit  of  gravelly 
soil.  Where  this  moraine  exists  the  face  of 
the  country  is  covered  with  "  kettle  holes  "  of 
all  sizes  and  shapes,  and  in  some  of  them  there 
are  small  lakes,  while  others  are  dry.  The 
great  chain  of  inland  lakes  that  are  found  in 
southern  Wisconsin  and  northern  Illinois  were 
formed  by  deposits  of  ice  that  had  been  cov- 
ered by  glacial  drift,  gravel  and  otherwise, 
brought  down  and  deposited  upon  these  masses 
of  ice  which  gradually  melted  away,  leaving  a 
depression  at  the  points  where  they  lay,  while 
the  drift  that  was  piled  around  them  loomed 
up  and  became  the  shores  of  the  lake.  This  is 
substantially  Dr.  Wright's  theory,  who  studied 
the  formation  of  these  "  kettle  holes  "  at  the 
mouth  of  the  Muir  glacier.  This  enthusiastic 
glacialist  has  spent  many  summers  tracing  the 
terminal  moraine  with  its  fringe  along  the 
lines  heretofore  indicated.  He  is,  therefore, 
entitled  to  speak  with  authority  on  matters  of 
glacial  action. 

The  part  of  the  country  that  has  been 
plowed  over  by  these  glaciers  is  called  the  gla- 
ciated area  and  the  rest  the  unglaciated.  The 


210  matured 

whole  of  North  America  north  of  the  line  of 
the  terminal  moraine  that  we  have  traced  is 
a  glacial  region,  with  the  exception  of  a  few 
hundred  square  miles  chiefly  in  Wisconsin, 
where  the  ice  seemed  to  have  parted  and 
passed  around  this  area,  coming  together 
again  on  the  south  side  of  it.  The  ice  prob- 
ably did  not  reach  the  extreme  limit  that 
shows  glacial  deposit,  but  undoubtedly  the 
effects  of  it  are  seen  for  some  distance  to  the 
south,  owing  to  the  fact  that  during  the  time 
it  was  melting  great  quantities  of  water  flowed 
away  from  the  extreme  edge  of  the  ice,  carry- 
ing with  it  more  or  less  of  the  glacial  drift, 
which  was  deposited  for  some  distance  to  the 
south.  When  the  ice  receded  it  undoubtedly 
paused  at  different  points,  where  it  remained 
stationary  for  a  long  period  of  time.  I  mean 
stationary  at  its  edges,  for  the  flow  of  ice  was 
continually  moving,  but  in  its  progress  south- 
ward it  came  to  a  point  where  the  heat  waa 
sufficient  to  melt  the  ice  as  fast  as  it  arrived 
at  that  point.  The  on-moving  ice  was  con- 
tinually bringing  with  it  the  debris  that  it  had 
gathered  up  at  different  points  on  its  journey, 
so  that  it  is  easy  to  see  how  these  moraines 
could  accumulate  to  a  greater  or  less  depth  at 
the  margin  of  the  ice  flow,  which  would  be  de- 
termined by  the  duration  of  the  period  it  re- 
mained stationary.  This,  however,  is  only 
one  factor,  as  the  surface  of  the  earth  in  some 


Evidences  of  an  1fce 

parts  of  the  country  would  be  more  easily 
picked  up  and  carried  than  in  others;  there- 
fore, the  drift  accumulated  much  more  rapidly 
in  some  sections  than  in  others. 

Another  factor  that  was  active  in  the  more 
rapid  accumulation  at  certain  points  was  the 
speed  at  which  the  ice  moved,  and  this  would 
be  determined  by  the  pressure  that  was  behind 
it,  and  there  would  always  be  lines  of  unequal 
pressure  existing  in  such  a  great  glacier  as 
must  have  existed  when  these  moraines  were 
formed. 

As  an  instance  of  the  difference  in  the  gla- 
cial deposits  that  are  made  in  different  periods 
during  the  time  of  the  melting  of  the  great  ice 
sheet  we  may  compare  the  Kettle  Moraines  of 
Wisconsin  with  the  clay  deposit  mixed  with 
broken  gravel  that  we  find  along  the  west  coast 
of  Lake  Michigan.  Those  whose  homes  are 
situated  between  Winnetka  and  Waukegan  on 
the  lake  shore  have  the  foundations  of  their 
houses  set  in  glacial  drift  that  was  shoved  into 
position  by  the  ice  during  the  glacial  period. 

Anyone  who  makes  an  examination  of  the 
bluffs  along  the  shore  of  this  lake  will  notice 
that  there  is  no  stratification  whatever  to  the 
deposit  such  as  will  always  be  found  in  an  un- 
glaciated  region.  Going  west  from  the  bluff 
a  few  miles  we  come  down  to  the  prairie  level, 
where  we  find  the  soil  of  an  entirely  different 
nature.  The  soil  of  the  prairies  of  Illinois 


212  matured  flfcfracles. 


and  Iowa  is  probably  to  a  great  extent  a  water 
deposit.  It  is  the  kind  we  find  in  the  bottom 
of  a  pond  that  has  stood  for  many  years,  and 
it  would  seem  that  at  some  period  all  this 
prairie  country  with  the  black  soil  was  the 
bottom  of  a  great  lake. 

The  facts  of  a  glacial  period  are  beyond 
question,  but  when  it  occurred,  and  how  it 
occurred  are  questions  that  many  have  tried  to 
answer.  So  far,  all  that  we  can  say  of  them 
is  that  some  of  them  are  shrewd  guesses.  The 
evidences  adduced  for  determining  the  time, 
are  the  erosion  caused  by  rivers  and  streams 
since  the  ice  subsided.  Some  of  the  rivers 
and  outlets  of  lakes  had  their  courses  changed 
by  the  action  of  the  ice,  so  that  when  it  sub- 
sided new  water  courses  were  formed,  and  the 
erosion  that  they  have  produced  from  that 
time  to  the  -present  furnishes  the  data  for  de- 
termining the  time  since  the  subsidence  of  the 
ice  at  any  particular  point.  For  instance, 
Niagara  Falls  was  undoubtedly  at  one  time 
situated  at  Queenstown,  a  number  of  miles  be- 
low its  present  position.  And  the  time  that  it 
has  taken  to  grind  out  the  great  gorge  that 
exists  between  that  point  and  the  present  falls 
is  approximately  a  measure  of  the  time  that 
has  elapsed  since  the  subsidence  of  the  ice  at 
that  point.  Various  estimates  have  been 
made  to  determinate  the  rate  of  erosion.  The 
earlier  ones  put  the  time  at  about  35,000  years. 


3£\>R>ence0  of  an  flee  B0e,          213 


But  there  are  later  investigators  who  make  the 
time  much  shorter,  not  over  10,000  years. 

So  much  for  the  time;  but  you  ask  What 
about  the  occasion,  or  cause  ?  This  is  a  ques- 
tion that  many  have  attempted  to  answer, 
there  having  been  eight  or  ten  theories  pro- 
mulgated with  regard  to  the  cause  of  the  gla- 
cial period,  but  no  one  of  them  is  entirely 
satisfactory,  and  only  two  or  three  of  them  are 
deserving  of  much  discussion.  It  is  always 
interesting  to  know  what  people  think,  how- 
ever, even  if  we  do  not  agree  with  them. 

The  first  theory  named  is  that  the  glacial 
period  is  due  to  the  decrease  of  the  original 
heat  in  our  climate.  This  theory  can  be  dis- 
missed by  saying  that  the  planet  was  cooling 
at  the  time  and  has  been  cooling  ever  since, 
and  that  the  reasons  for  an  ice  age  are  greater 
now  than  then,  on  that  theory.  Another 
theory  assumes  that  at  some  former  period 
there  was  a  greater  amount  of  moisture  in  the 
atmosphere  ;  while  this  of  course  would  be  the 
occasion  for  greater  precipitation  of  snow,  it 
does  not  account  for  the  changing  conditions 
that  would  produce  the  ice  effect.  That  there 
was  a  preglacial  period  there  is  abundant  evi- 
dence, in  buried  forests,  the  filling  up  and 
changing  of  river  beds,  and  other  evidences 
that  will  be  referred  to  further  on.  This 
theory,  unmodified  and  stated  broadly,  is  not 
satisfactory.  Another  way  of  accounting  for 


214  Nature's  .fllMractee. 

the  glacial  period  is  the  change  in  the  distri- 
bution of  land  and  water,  which  is  supposed  to 
affect  the  distribution  of  heat  over  the  earth's 
surface.  There  is  much  in  this  theory  that 
commends  itself  as  plausible.  Another  theory 
supposes  that  the  land  in  northern  Europe  and 
America  was  elevated  to  a  higher  level  at  that 
time  than  it  is  now.  Others  attribute  it  to 
variation  of  temperature  in  space  and  of  the 
amount  of  heat  radiated  by  the  sun.  The  final 
theory  for  accounting  for  the  ice  age  is  at- 
tributed to  what  is  termed  the  precession  of 
the  equinoxes.  In  short,  the  precession  of  the 
equinoxes  means  that  the  division  between 
summer  and  winter  is  changing  gradually,  so 
that  during  a  period  of  10,500  years  the  sum- 
mers are  growing  longer  in  the  northern  hemi- 
sphere and  the  winters  shorter.  We  are  now 
in  the  period  of  long  summers,  but  in  another 
10,000  years  we  shall  be  in  the  period  of  short 
summers  and  long  winters.  This  difference  of 
time  between  the  winters  and  the  summers  is 
supposed  to  be  sufficient  to  change  the  thermal 
conditions  sufficiently  to  produce  an  ice  age. 

It  is  true  that  the  conditions  now  are  very 
evenly  balanced,  so  much  so  that  in  Switzer- 
land the  glaciers  will  increase  for  some  years 
together,  when  the  conditions  will  change, 
causing  them  to  gradually  recede.  Several  of 
the  theories  that  have  been  advanced  present 
evidences  that  are  entitled  to  careful  consider- 


of  an  flee  Bge.          215 


ation,  but  none  of  them  can  be  said  to  be  en- 
tirely satisfactory.  It  is  well  known  that  the 
chief  factors  in  the  production  of  glaciers  are 
moisture  and  cold.  Cold  alone  is  not  suffi- 
cient; neither  is  moisture,  unless  we  can  pre- 
cipitate it  in  the  form  of  snow.  Cold  is  op- 
posed to  the  production  of  moisture,  and  this 
is  a  flaw  in  the  argument  presented  by  the  last 
theory,  unless  we  can  couple  with  it  another 
set  of  conditions  which  we  will  discuss  later. 

The  solution,  if  it  is  ever  reached,  is  perhaps 
more  likely  to  be  found  in  the  realm  of  meteor- 
ology than  geology. 

It  is  unnecessary  to  change  the  conditions 
of  temperature  or  the  amount  of  moisture  now 
existing  in  order  to  produce  the  great  glacier 
again,  provided  this  moisture  could  be  precipi- 
tated, enough  of  it,  in  the  right  place  as  snow. 
For  instance,  if  in  Switzerland,  where  the  con- 
ditions are  nearly  balanced,  the  annual  pre- 
cipitation could  be  slightly  increased  we  should 
have  a  condition  that  would  precipitate  more 
snow  in  winter  than  would  melt  in  summer. 
And  the  glaciers  would  gradually  accumulate 
in  size  until  they  would  fill  the  valleys  and 
gorges  to  the  same  extent  as  formerly  pre- 
vailed. There  only  needs  to  be  such  a  change 
in  the  meteorological  conditions  as  will  cause 
a  greater  precipitation  in  that  part  of  the 
globe  favorable  to  glaciers,  as,  for  instance,  in 
the  northern  part  of  North  America  toward 


216  lRature'0  /HMracles. 

Alaska.  This  might  be  produced  hy  a  change 
in  the  conditions  of  the  equatorial  current,  so 
that  evaporation  would  be  more  rapid  in  the 
northern  Pacific  than  it  now  is.  When  we 
consider  that  evaporation  increases  in  pro- 
portion as  the  heat  increases,  we  can  see  that 
heat  is  just  as  important  a  factor  in  the  pro- 
duction of  glaciers  as  cold.  If  evaporation 
could  be  increased  in  the  Pacific  Ocean  west 
of  Alaska,  which  would  be  carried  by  the  wind 
over  the  mountains  upon  the  land,  and  pre- 
cipitated as  snow,  the  great  glaciers  in  that 
region  would  begin  to  grow  instead  of  gradu- 
ally receding,  as  is  the  case  at  present,  and 
this  without  any  change  in  the  temperature  of 
the  world  as  a  whole  or  in  the  amount  of  heat 
received  from  the  sun.  One  can  readily  see 
how  changes  in  the  elevation  of  the  bottom  of 
the  ocean  would  have  such  an  effect  upon  the 
tropical  stream  as  would  either  increase  or  de- 
crease the  temperature  of  the  thermal  river 
that  flows  up  the  western  coast  of  Alaska. 

Whatever  may  have  been  the  cause  that 
created  the  great  ice  age  in  North  America, 
so  that  a  sheet  of  ice  covered  considerably 
more  than  half  of  the  continent,  there  is  no 
doubt  in  regard  to  the  fact  of  the  existence  of 
such  an  age,  and  it  will  be  interesting  to  study 
some  of  the  physical  changes  that  have  been 
made  by  the  ice  at  that  period  on  the  surface 
of  the  glaciated  area. 


CHAPTEE  XXVII. 

GLACIAL  AND  PREGLACIAL   LAKES  AND 
RIVERS. 

Since  the  recession  of  the  ice,  preglacial 
lakes  have  been  filled  up  and  are  now  dry  land, 
and  river  beds  have  been  changed  so  that 
new  channels  have  been  cut  and  new  lakes 
have  been  formed.  Even  the  imagination, 
that  wonderful  architect,  with  all  its  tenden- 
cies to  exaggeration,  palls  in  its  attempt  to 
give  expression  in  measured  quantities  to  the 
mighty  power  exerted  by  the  great  glacier  or 
combination  of  glaciers  that  existed  in  com- 
paratively recent  times.  I  say  recent  times, 
because  even  10,000  years  is  only  a  mere  point 
of  time  when  compared  with  the  actual  age  of 
our  globe. 

Some  years  ago,  in  company  with  Dr. 
Wright,  author  of  the  "Ice  Age  in  North 
America,"  I  visited  Devil's  Lake  near  Bara- 
boo,  Wis.  At  this  point  are  striking  evidences 
of  the  work  of  the  ice  age.  Before  the  glacial 
period  the  Wisconsin  River  made  a  detour 

217 


218  future's 

some  miles  west  of  its  present  channel  through 
the  high  hills  in  the  region  of  Baraboo.  The 
hills  on  each  side  of  Devil's  Lake  are  very  pre- 
cipitous and  are  formed  almost  entirely  of 
rocks.  The  river  at  that  point  passed  between 
two  of  these  hills.  When  the  ice  flowed  down 
it  surrounded  these  hills,  yet  did  not  sweep 
over  their  tops,  but  left  great  piles  of  glacial 
drift,  both  at  the  points  where  the  river  chan- 
nel entered  the  hills  and  where  it  emerges 
from  them.  The  channel  between  the  hills 
was  protected  and  not  filled  with  the  debris. 
Therefore  a  deep  basin  was  left,  which  is  kept 
filled  by  the  watershed  furnished  by  the  sur- 
rounding hills.  This  lake  recedes  many  feet 
during  the  summer,  but  it  is  again  filled  up 
by  the  rains  and  snows  of  winter.  There  is  no 
considerable  stream  either  flowing  into  or  out 
from  it.  It  is  a  lake  formed  by  the  glaciers, 
but  in  a  different  way  from  those  in  the  gravel 
deposits  at  other  parts  of  southern  Wisconsin 
and  northern  Illinois. 

There  are  hundreds  and  perhaps  thousands 
of  lakes  that  have  been  formed  in  one  way  or 
another  through  the  power  of  glacial  action. 
These  smaller  inland  lakes,  so  many  of  which 
are  seen  in  northern  Illinois,  southern  Wis- 
consin, and  Minnesota,  are  due  almost  entirely 
to  the  great  deposits  of  glacial  drift  that  have 
been  transported  with  the  ice.  Wherever 
these  "  kettle  holes  "  are  found  large  bodies  of 


<3lacfal  anfc  ipreglacial  Xafcee.      219 

ice  have  become  anchored,  while  the  ice  behind 
it  has  carried  the  drift  until  it  is  covered  over 
and  piled  up  at  the  sides.  When  these  ice 
mountains  melted  away  depressions  were  left 
which  in  some  cases  have  resulted  in  lakes,  and 
in  others  simply  dry  kettle  holes.  This 
process  has  been  hinted  at  in  a  former  chapter, 
but  we  give  it  here  as  one  of  the  kinds  of  lakes 
formed  during  the  glacial  period.  They  are 
found  everywhere  that  glacial  action  has  pre- 
vailed. They  are  found  in  great  abundance 
in  some  parts  of  New  England  on  the  margin 
of  the  terminal  moraine.  These  lakes,  how- 
ever, are  comparatively  insignificant  as  com- 
pared with  the  great  inland  seas  like  Lake 
Superior  and  Lake  Michigan,  that  undoubt- 
edly owe  their  origin  largely  to  the  ice  age. 

There  are  other  factors,  however,  that  enter 
into  the  formation  of  the  great  chain  of  lakes 
on  the  northern  boundary  of  the  United 
States  besides  those  mentioned,  that  have 
brought  into  existence  the  smaller  inland 
lakes. 

Glacial  lakes  may  be  divided  into  three 
classes.  Those  found  in  the  "kettle  holes" 
of  the  terminal  or  medial  moraines,  and  those 
that  are  formed  by  the  deposition  of  the  gla- 
cial drift,  as,  for  instance,  Devil's  Lake,  and 
those  that  are  caused  by  ice  forming  dams 
across  the  valley  of  a  river  that  lasted  only 
during  the  ice  age.  In  some  lakes  of  the 


220  Dature'6 

second  class  erosion  undoubtedly  entered  into 
their  formation  as  well  as  the  piling  up  of 
glacial  drift. 

In  order,  however,  that  we  may  understand 
more  fully  the  formation  of  these  greater  lakes 
it  will  be  necessary  for  us  to  go  back  and  ex- 
amine the  conditions  that  seem  to  have  existed 
before  the  glacial  period. 

It  is  a  fact  well  known  that  continents  have 
periods  of  elevation  and  depression.  There  is 
abundant  evidence  that  the  northern  portion 
of  the  North  American  continent  was  elevated 
to  a  much  higher  level  in  preglacial  times  than 
it  occupies  now.  This  is  evidenced  in  very 
many  ways  by  sounding  the  depths  of  old  river 
beds  now  filled  with  glacial  debris.  The  old 
beds  show  unmistakable  evidences  of  having 
been  worn  down  to  their  present  level  by  the 
action  of  running  water.  They  also  prove  to 
be  many  feet  below  the  present  sea-level.  This 
fact  seems  to  be  sufficient  to  prove  the  theory 
of  a  higher  elevation  of  the  North  American 
continent  in  preglacial  times.  It  should  be 
said  here  that  undoubtedly  the  constant  filling 
up  of  the  ocean  with  the  drift  carried  down  by 
the  rivers  has  somewhat  raised  its  level,  but 
hardly  to  the  extent  indicated  by  the  old  river 
beds.  The  question  naturally  arises,  Where 
did  all  the  dirt  come  from  to  fill  up  these  great 
river  beds  and  change  the  whole  topography 
of  the  northern  half  of  the  continent?  Dr. 


<3ladal  and  ipregladal  Xafees,       221 

Wright  estimates  that  there  is  not  less  than 
1,000,000  square  miles  of  territory  in  North 
America  covered  with  glacial  debris  to  an 
average  depth  of  50  feet.  Of  course,  the 
depth  varies  in  different  places  from  a  few 
inches  to  several  hundred  feet.  Of  the  carry- 
ing power  of  these  great  glaciers  we  will  speak 
more  fully  in  a  future  chapter.  In  preglacial 
times  the  watershed  of  the  Mississippi  and  of 
the  great  rivers  east  of  the  Alleghany  Moun- 
tains, the  Susquehanna  and  Hudson,  extended 
probably  farther  north  than  it  does  to-day. 
The  larger  portion  of  the  drainage  area  that 
now  finds  an  outlet  through  the  River  St.  Law- 
rence at  one  time  undoubtedly  drained  off 
through  the  Mississippi  Valley  into  the  Gulf 
and  the  Valley  of  the  Mohawk  into  that  of  the 
Hudson. 

It  is  supposed  by  those  who  have  made  this 
branch  of  geology  a  study  that  prior  to  the 
glacial  period  a  river  flowed  down  through 
Lake  Superior,  which  connected  with  Lake 
Michigan  at  a  point  near  its  present  outlet  at 
Sault  Ste.  Marie,  the  channel  of  the  river 
passing  down  through  what  is  now  the  bot- 
tom of  Lake  Michigan,  which  had  an  outlet  at 
the  head  of  the  lake  near  Chicago  and  flowed 
off  into  the  Mississippi  River.  All  of  the  lake 
bottoms  of  this  great  chain,  with  the  exception 
of  Lake  Erie,  are  now  below  sea-level.  The 
reason  for  this  exception  will  appear  further 


matured  /l&frades, 

on.  Before  the  ice  age  there  was  supposed  to 
be  no  connection  between  Lake  Michigan  and 
Lake  Huron,  as  there  is  now,  through  the 
Straits  of  Mackinac. 

Another  preglacial  river  had  its  rise  in  the 
region  of  Lake  Huron  and  flowed  through  an 
old  river  bed  extending  from  the  Georgian 
Bay  in  a  southeasterly  direction  through  the 
province  of  Ontario,  and  emptied  into  the 
present  Lake  Ontario.  From  Lake  Ontario 
there  is  an  old  river  bed  running  through  the 
Valley  of  the  Mohawk  which  empties  into  the 
Hudson  at  Troy.  Neither  of  these  two  rivers, 
having  their  sources  in  the  north,  found  an 
outlet  through  the  present  St.  Lawrence 
River.  During  the  time  of  the  glacial  period 
there  is  evidence  that  there  was  more  than  one 
center  of  snow  and  ice  accumulation  and  each 
of  these  great  centers  probably  had  several 
subcenters.  This  theory  has  color  given  to  it 
by  the  directions  of  movement  shown  by  the 
glacial  drift. 

The  rounded  appearance  of  bowlders  was 
caused  by  the  grinding  action  of  the  ice. 
These  bowlders,  when  they  were  first  torn  from 
their  rocky  beds  by  the  irresistible  power  of 
ice  pressure,  were  rough  and  jagged  in  shape, 
the  same  as  any  rock  would  be,  torn  from  a 
quarry  by  a  blast  They  have  been  smoothed 
and  rounded  by  rubbing  against  the  moving 
ice  and  against  each  other  in  the  progress  of 


(Blacfal  anD  ipregiactal  iafces,       223 

their  long  journey  from  their  original  homes. 
Where  their  home  was  the  geologist  can  im- 
mediately tell  upon  examination.  It  is  only 
necessary  then  to  examine  the  bowlders  of  any 
particular  locality  to  determine  the  direction 
of  the  ice  flow  at  that  point. 

There  seem  to  have  existed  centers  of  ice 
accumulation  to  the  north  of  all  of  the  great 
lakes.  And  when  they  had  grown  to  a  suffi- 
cient height  they  joined  at  their  edges,  mak- 
ing one  grand  glacier,  the  movements  of  which 
were  the  resultant  of  the  combined  pressure 
exerted  by  these  great  centers  of  power,  so  that 
all  of  North  America  north  of  the  line  of  the 
terminal  moraine,  with  the  exception  of  a 
small  area  (heretofore  noted)  chiefly  in  Wis- 
consin, became  covered  with  one  vast  sheet  of 
ice. 

The  glacier  north  of  Lake  Superior  widened 
out  the  old  river  bed  by  a  process  of  erosion 
to  its  present  width. 

There  may  have  existed  something  of  a  lake 
in  preglacial  times,  through  which  the  river 
ran,  but  it  undoubtedly  owes  its  present  width 
to  the  grinding  action  of  the  irresistible  ice- 
bergs and  the  piling  up  of  debris  on  the  shores. 
The  river  bed  was  filled  up  by  a  glacial  drift  at 
the  point  of  its  present  outlet  until  the  lake 
was  raised  in  its  level  much  higher  than  that 
of  Lake  Michigan.  Another  glacier  plowed 
down  through  Lake  Michigan,  widening  it  out 


224  matured  /ifciracles, 


to  its  present  dimensions,  while  the  glacial 
drift  was  deposited  at  what  is  now  the  head  of 
the  lake,  filling  up  the  old  outlet  and  thus 
making  a  great  dam.  The  damming  up  of 
these  great  water  courses  was  another  cause 
for  increasing  the  width  of  these  lakes.  In  a 
similar  way  Lake  Erie  was  formed.  It  is  sup- 
posed, however,  that  this  lake  is  entirely  the 
product  of  glacial  action,  as  there  is  no  evi- 
dence of  an  old  river  bed  in  its  bottom;  be- 
sides, it  is  much  shallower  than  the  other 
lakes.  The  same  action  that  formed  Lake 
Erie  filled  up  the  old  river  bed  running 
through  the  province  of  Ontario,  so  that  when 
the  ice  receded  Lake  Erie  became  the  new 
channel  for  the  old  river.  The  same  process 
filled  up  the  Valley  of  the  Mohawk  to  more 
than  100  feet  in  depth  and  also  raised  the 
Valley  of  the  Hudson.  This  caused  the  new 
channel  to  be  made  through  the  Niagara  Eiver 
and  a  new  route  to  the  ocean  for  the  drainage 
of  all  the  chain  of  lakes  through  the  St.  Law- 
rence. It  will  be  seen  that  the  bottoms  of  all 
of  these  great  lakes  to  a  certain  extent  were 
worn  out  by  the  action  of  running  water,  ex- 
cept Erie.  The  great  glaciers  widened  them 
out,  and  in  the  case  of  Lake  Erie  scooped  it 
out.  At  the  same  time  it  built  great  dams 
across  the  outlets  which  raised  the  surface  of 
the  water  to  a  much  higher  level  and  caused 
them  to  form  new  outlets,  thus  changing  the 


(Slacfal  anD  ipreglacial  ftafces,       225 

whole  face  of  the  country  over  which  the  ice 
drifted. 

The  glaciated  region  of  North  America  is 
among  the  most  productive  in  the  world,  and 
in  many  respects  presents  a  most  pleasing 
landscape. 

Other  lakes  besides  these  mentioned  have 
been  formed  during  the  ice  period  through 
blocking  the  course  of  a  river  by  the  ice  itself. 
Dr.  Wright,  during  the  time  he  traced  out  the 
line  of  the  terminal  moraine,  discovered  that 
the  ice  sheet  crossed  the  Ohio  Kiver  at  a  point 
near  Cincinnati,  where  there  is  a  great  bend 
to  the  northward  in  the  river.  With  the  ex- 
ception of  this  point  and  perhaps  another 
point  below,  the  edge  of  the  great  ice  sheet 
kept  a  little  north  of  the  Ohio  Kiver.  At  this 
point,  however,  the  ice  seems  to  have  filled  the 
valley  from  hill  to  hill,  which  very  naturally 
would  form  a  great  dam  or  lake  in  the  Ohio 
Valley.  Of  course  such  a  lake  could  not  be 
permanent,  because,  when  the  ice  melted  away, 
it  again  opened  the  channel  and  allowed  the 
water  to  flow  off. 

Some  years  before  this  discovery  was  made 
there  were  terraces  found  along  the  banks  of 
the  Ohio  Eiver  and  its  tributaries  that  had 
been  the  subject  of  much  speculation.  It  is 
well  known  that  by  the  action  of  water  from 
rainfall,  earth,  gravel,  and  other  debris  will 
wash  down  the  side  of  a  hill  or  mountain  until 


226  matured  /BMracles, 

it  strikes  a  water  level,  and  there  it  will  build 
out  a  terrace  near  the  level  of  the  water  sur- 
face. The  width  of  these  terraces  will  be  de- 
termined by  the  time  the  water  has  stood  at 
that  level  and  the  extent  and  nature  of  the 
soil  from  which  the  debris  comes.  The  evi- 
dences that  are  cited,  pro  and  con,  would  fill  a 
small  volume,  but  it  is  sufficient  to  say  here 
that  the  sum  of  the  evidence  goes  to  show  that 
there  was  an  ice  dam  formed  at  a  point  near 
Cincinnati  and  that  it  was  maintained  for  a 
considerable  period  of  time.  Terraces  were 
formed  running  up  the  Ohio  and  its  tribu- 
taries corresponding  to  the  level  that  the  water 
must  have  risen  to  if  the  valley  were  filled  up 
with  ice.  These  facts,  taken  with  the  greater 
fact  that  the  ice  sheet  actually  did  cross  the 
Ohio  Valley  into  Kentucky,  as  is  shown  by  the 
terminal  moraine,  seems  to  prove  conclusively 
the  existence  of  such  a  lake  during  the  period 
that  the  ice  rested  at  its  extreme  limit.  The 
fact  that  in  some  places  successive  terraces  are 
found  does  not  disprove  the  theory,  because  it 
is  more  than  likely  that  when  the  ice  receded 
it  did  so  in  successive  stages,  remaining  at  dif- 
ferent positions  for  a  considerable  length  of 
time.  There  is  abundant  proof  of  this  in  the 
successive  moraines  and  also  in  the  formation 
of  successive  terraces.  Some  of  these  terraces 
could  have  been  formed  from  other  causes. 
It  does  not  require  any  great  stretch  of  the 


(Slacial  and  Oreglacial  3lafces,       227 

imagination  to  understand  how  numerous 
lakes,  much  larger  than  any  at  the  present  day, 
may  have  extended  over  large  portions  of  the 
West  and  Northwest  during  the  period  that 
the  ice  was  receding.  The  ice  did  not  stand 
with  an  even  thickness  over  the  surface  of  the 
glaciated  area,  but  at  some  points  it  moved 
down  in  great  lobes,  which  marked  the  lines  of 
greatest  pressure  as  well  as  the  greatest  ac- 
cumulation. As  the  ice  melted  away,  the 
thick  bodies  of  ice  might  be  many,  many  years 
in  melting,  and  they  might  block  the  outlet  to 
a  very  extensive  drainage  area  and  thus  form 
a  great  inland  sea  from  the  vast  amounts  of 
water  that  would  come  from  the  melting  ice. 

All  of  the  region  about  Winnipeg,  in  the 
Red  River  country,  covering  great  areas  of 
hundreds  of  miles  in  extent,  is  a  level  plain 
only  lacking  the  coloring  to  give  to  one  pass- 
ing through  it  the  effect  of  a  great  unruffled 
sea.  There  is  no  doubt  but  that  all  of  this 
region  was  the  bottom  of  a  great  lake  at  some 
period  when  the  ice  was  receding.  And  this 
accounts  for  the  great  depth  of  black  soil  that 
we  find  in  this  and  other  regions.  The  soil 
was  a  water  deposit,  such  as  may  be  found  in 
the  bottom  of  any  shallow  lake  or  pond  to-day, 
and  thus  many  thousand  years  ago  provision 
was  made  for  the  fertile  areas  which  to-day 
are  feeding  the  world  with  wheat. 

We  can  imagine  that  during  this  period  the 


228  flature'e 

water  that  flowed  off  through  the  great  Miss- 
issippi must  have  been  of  enormous  volume  as 
compared  to  the  present  time.  A  large  por- 
tion of  the  delta  of  the  Mississippi  which  now 
is  a  part  of  the  States  of  Louisiana  and  Miss- 
issippi was  carried  down  during  the  ice-melt- 
ing period.  Dr.  Wright — as  we  have  before 
stated — has  estimated  that  there  are  a  million 
square  miles  of  country  that  has  been  covered 
to  an  average  depth  of  fifty  feet  with  glacial 
drift.  A  very  large  amount  of  the  earth  that 
was  spread  over  the  northern  portion  of  the 
United  States  by  leveling  down  hills  and 
mountains  in  the  northern  country  and  scoop- 
ing out  the  great  lakes  has  been  carried  much 
farther  than  to  the  margin  of  the  ice  sheet. 
And  I  have  no  doubt  but  that  a  great  portion 
of  Louisiana  and  western  Mississippi  is  made 
of  earth  carried  down  largely  during  the 
period  of  melting  ice  and  deposited  in  this 
great  delta. 

Imagine  the  effect  that  would  be  produced 
by  the  giving  way  of  an  ice  dam  or  a  great 
number  of  them  at  different  periods,  that 
would  allow  a  body  of  water  as  large  or  larger 
than  Lake  Michigan  to  be  drained  off  in  a 
comparatively  short  time.  When  we  think  of 
it  in  this  light  the  great  delta  of  the  Miss- 
issippi is  easily  accounted  for. 

There  are  evidences  of  a  great  lake  in  the 
Red  River  country  of  the  Northwest  that  is 


(Blacial  anfc  preglacfal  SLafces,       229 

much  larger  than  any  of  our  greatest  lakes. 
The  shores  of  this  lake — the  bed  of  which  is 
now  dry  land  and  the  heart  of  a  great  agricul- 
tural region — are  well  defined  and  have  been 
surveyed  and  mapped  out.  When  this  great 
body  of  water  was  released  it  was  to  the  north- 
ward. For  this  reason  it  was  undoubtedly 
held  for  a  much  longer  time  than  some  of  the 
lakes  to  the  southward  where  the  ice  melted 
sooner. 


CHAPTEK  XXVIII. 

SOME    EFFECTS    OF    THE    GLACIAL    PEKIOD. 

There  is  a  wonderfully  interesting  effect 
produced  by  the  action  of  water  during  the 
subsidence  of  a  glacier  at  Lucerne,  Switzer- 
land. Some  years  ago  there  was  discovered 
under  a  pile  of  glacial  drift  at  the  edge  of  the 
town  of  Lucerne  a  number  of  deep  holes  worn 
in  a  great  ledge  of  rocks  that  crop  out  at  that 
point.  One  of  these  pot-holes  having  been  dis- 
covered, excavations  were  continued  until  a 
large  number  of  them  were  unearthed  of  vari- 
ous shapes  and  sizes.  I  had  the  pleasure  of  in- 
specting some  of  them  in  the  year  1881.  They 
are  situated  within  an  in  closure  called  the 
Garden  of  the  Glaciers.  Some  of  these  holes 
are  twenty  to  thirty  feet  in  diameter,  and  the 
same  depth.  There  are  others  that  are  smaller 
in  size,  but  all  of  them  possess  the  same  gen- 
eral characteristics. 

In  the  bottom  of  each  one  was  found  a 
bowlder,  and  in  one  or  two  cases  two  of  them. 
The  action  of  the  water  had  given  these  bowl- 
ders a  gyratory  motion,  which  gradually  wore 


Effects  of  tbe  Olacfal  period      231 

away  the  rock  underneath  until  round  holes 
were  formed  to  the  size  and  depth  heretofore 
mentioned.  Where  there  was  only  a  single 
bowlder  the  holes  were  almost  perfectly  round, 
but  where  there  was  more  than  one  bowlder 
the  holes  were  sometimes  in  an  oblong  shape. 
The  bowlders  were  worn  down  to  a  very  small 
size  in  most  cases,  and  were  round  and  smooth. 
The  probabilities  are  that  when  the  action  first 
began  these  bowlders  were  large  and  of  irregu- 
lar shape.  They  must  have  been,  in  order  to 
do  the  enormous  amount  of  grinding  that 
some  of  them  did  to  produce  excavations  in 
the  solid  rock  with  a  diameter  of  thirty  feet 
and  a  depth  about  the  same.  The  bottoms 
were  round  like  an  old-fashioned  pot,  and  the 
insides  polished  perfectly  smooth.  This  was 
purely  an  effect  of  the  tumbling  about  of 
the  bowlders  by  the  running  water  from  the 
melting  ice  of  the  great  glacier  that  covered 
that  region  some  time  in  the  long  ago. 

There  are  other  effects  produced  in  rocks 
during  the  ice  flow  in  North  America  that  are 
very  interesting.  Great  grooves  are  formed 
in  the  rocks,  in  many  cases  running  for  long 
distances,  that  have  been  worn  in  by  the  cut- 
ting power  of  the  great  ice  sheet  during  the 
progress  of  its  movement.  There  is  a  great 
groove  to  be  seen  at  Kelly's  Island  in  Lake 
Erie.  It  will  be  remembered  that  this  lake  is 
supposed  to  have  been  formed  entirely  by  the 


232  matured 

ice  of  the  glacial  period.  In  its  movement 
across  the  country  which  is  now  covered  by  the 
lake  the  ice  encountered  a  huge  rock  forma- 
tion at  Kelly's  Island.  Great  V-shaped 
grooves  were  cut  through  this  rock  by  the 
action  of  the  ice,  deep  enough  for  a  man  to 
stand  in.  In  other  places  the  rock  was  planed 
off  in  the  form  of  a  great  molding,  a  number 
of  feet  wide,  with  the  same  smoothness  and  ac- 
curacy as  though  done  by  a  machine. 

Another  effect  of  the  glacial  period  has  been 
the  creation  of  numerous  waterfalls  through- 
out the  glaciated  area.  The  most  notable  in- 
stance is  that  of  the  Falls  of  Niagara. 

In  preglacial  times  the  beds  of  all  rivers  and 
water  courses  had  worn  down  to  an  even  slope, 
so  that  there  were  very  few,  if  any,  waterfalls 
such  as  we  have  to-day.  As  we  have  before 
stated,  Niagara  Eiver  as  well  as  the  St.  Law- 
rence Eiver  is  a  new  outlet  for  the  drainage  of 
the  great  lakes.  A  part  of  this  drainage  for- 
merly had  its  outlet  through  the  Mohawk  Val- 
ley into  the  Hudson,  which  is  now  filled  up 
with  glacial  drift.  The  evidence  is  so  con- 
clusive that  it  is  no  longer  doubted  that  the 
Niagara  Eiver  dates  from  the  time  that  the 
ice  receded  from  that  point.  When  the  water 
first  began  to  flow  through  this  new  channel 
it  plunged  over  the  high  rocky  cliff  at  Queens- 
town,  and  from  that  time  to  this  it  has  been 
wearing  its  way  back  to  the  present  position  of 


Effects  ot  tbe  Glacial  ipcrfo^      233 

Niagara  Falls,  a  distance  of  about  seven  miles. 
A  vast  amount  of  interest  centers  about  this 
river  because  it  is  the  best  evidence  we  have 
of  the  time  that  has  expired  since  the  glacial 
period.  A  great  deal  of  study  has  been  given 
to  determine  the  amount  of  erosion  at  the  Falls 
during  a  year's  time.  If  this  could  be  accu- 
rately determined,  then  by  measuring  the  dis- 
tance from  the  present  falls  to  Queenstown, 
we  could  easily  determine  the  number  of  years 
since  the  ice  period.  It  is  difficult  to  deter- 
mine, for  the  conditions  may  have  changed; 
for  instance,  the  rock  at  the  Falls  to-day  is 
said  to  be  harder  than  it  is  further  down  to- 
ward Queenstown.  The  estimates  vary  from 
35,000  years  to  10,000  years— that  is,  from  a 
rate  of  erosion  of  five  feet  to  one  foot,  per  year. 
Every  science  is,  nearly  or  remotely,  related 
to  every  other  science.  If  we  could  determine 
ac  urately  the  date  of  the  ice  period  it  would 
se  tie  a  whole  lot  of  other  questions  that  are 
re  ated  to  it,  and  one  of  them  is  the  antiquity 
o:  man.  Many  stone  implements  such  as  were 
n.ade  and  used  by  the  aborigines  have  been 
found  at  various  times  buried  deeply  under 
tne  glacial  drift.  These  finds  have  occurred 

o  often  that  there  no  longer  remains  a  doubt 
but  that  a  race  of  men  existed  on  this  conti- 

lent  in  preglacial  times.  There  are  evidences 
that  at  a  time  long  ago  the  temperate  zone  ex- 
tended far  north  of  this,  and  it  is  not  impos- 


234  IFUture'0  /llMracles, 

sible  that  what  is  now  the  continent  of  Asia 
and  that  of  North  America  were  joined.  In 
fact,  they  come  very  close  together  to-day  at 
Bering  Strait.  If  such  were  the  case  this  con- 
tinent could  have  been  inhabited  from  the  old 
world  by  ^an  overland  route.  This,  however, 
is  mere  speculation.  There  are  a  number  of 
factors  that  are  taken  into  account  in  deter- 
mining the  period  of  the  ice  age  besides  the 
Niagara  Eiver  and  the  Falls.  The  Falls  of  St. 
Anthony  at  Minneapolis  (which  like  the  Ni- 
agara is  a  creature  of  the  ice  age),  the  wear  of 
water  on  the  shores  of  the  great  lakes,  the 
newness  of  the  rocks  that  are  piled  up  on  the 
terminal  moraines,  all  point  to  a  much  shorter 
period  since  the  ice  age  than  it  used  to  be  sup- 
posed, and  indicate  that  the  time  does  not  ex- 
ceed 10,000  years. 

To  the  ordinary  mind  the  ice  age  no  doubt 
seems  like  a  myth,  but  to  the  man  of  science 
who  has  made  a  study  of  all  of  these  evidences 
it  is  as  real  as  any  fact  in  history,  and  much 
more  real  than  some  of  the  history  we  read. 
In  the  former  case  we  are  dealing  with  evi- 
dences that  appeal  to  our  senses,  while  in  the 
latter  we  are  dealing  with  the  recollections  of 
men  concerning  what  purport  to  have  been 
actual  transactions,  and  we  know  enough  about 
the  human  mind  to  make  it  difficult  sometimes 
to  draw  the  line  between  the  actual  and  the 
imaginary. 


Effects  of  tbe  Glacial  period      235 

The  glacial  period  is  not  only  closely  re- 
lated to  the  topography  of  North  America  and 
parts  of  Europe  in  the  changing  of  river  beds, 
the  formation  of  lakes,  the  transportation  of 
rock,  the  grinding  down  of  mountains  and 
spreading  the  debris  over  thousands  of  miles 
in  extent,  but  it  is  related  in  an  intimate  way 
to  many  of  the  sciences,  such  as  botany  and 
zoology.  A  study  of  the  flight  of  animals  and 
plants  in  front  of  the  great  advancing  ice 
sheet  is  a  subject  of  intense  interest.  The 
migration  of  great  forests  would  seem  to  be  an 
impossible  thing  when  viewed  from  the  stand- 
point of  a  casual  observer.  It  is  true  that  in- 
dividual trees  could  not  take  themselves  up 
and  move  forward  in  advance  of  the  oncoming 
ice,  but  they  could  and  did  send  their  children 
on  ahead,  and  when  the  ice  had  overtaken  the 
children  there  were  still  the  children's  children 
ad  infinitum. 

By  an  examination  of  the  map  it  will  be 
seen  that  the  land  gathers  about  the  north 
pole,  while  the  south  pole  is  surrounded  chiefly 
by  great  oceans.  As  we  have  hinted  before,  in 
preglacial  times  the  temperate  zone  extended 
much  farther  north  than  it  does  to-day,  and 
north  of  that  there  was  an  arctic  zone  (which 
to-day  is  largely  covered  with  ice  sheets), 
where  forests,  plants,  and  animals  flourished 
that  were  fitted  for  an  arctic  climate.  When 
the  glacial  period  set  in  and  the  ice  sheet  be- 


236  feature's  AMracles* 

gan  its  southern  journey  this  zone  or  climate 
was  moved, southward  in  front  of  the  ice,  thus 
forming,  as  it  were,  a  moving  zone  whose  cli- 
matic conditions  were  similar  to  those  of  the 
arctic  regions  (at  least  so  far  as  temperature 
was  concerned)  in  preglacial  times.  The  ice 
movement  was  so  gradual  that  time  was  given 
for  forests  to  spring  up  in  advance  of  it  that 
moved  southward  at  about  the  same  rate  as 
that  of  the  moving  ice.  Undoubtedly  the  aver- 
age movement  was  very  slow  and  was  probably 
thousands  of  years  reaching  its  southernmost 
limit,  which  is  now  marked  by  the  terminal 
moraine.  Thus  it  will  be  seen  that  while  the 
individual  trees  and  plants  could  not  move, 
the  forest  as  a  whole  could.  It  was  gradually 
being  cut  down  on  its  northern  limit  and  as 
gradually  it  grew  up  on  the  southern  limit  of 
the  zone;  the  ice  movement  being  so  slow  that 
the  young  tree  of  to-day  on  the  southern  limit 
becomes  a  full-grown  king  of  the  forest  by  the 
time  the  relentless  icebergs  reach  it  and  cut  it 
down  and  thus  the  process  went  on  until  the 
plants,  trees,  and  animals  of  the  arctic  region 
were  driven  hundreds  of  miles  south  of  the 
great  chain  of  lakes  on  the  northern  boundary 
of  the  United  States. 

Many  of  the  animals  of  preglacial  times 
were  unable  to  stand  the  strain  of  the  ever- 
changing  climatic  conditions  and  have  become 
extinct,  but  their  fossil  remains  are  left  to  tell 


Effects  of  tbe  (Blacfal  fceriofc.      237 

the  story  to  the  present  and  future  ages. 
Much  of  the  history  of  those  times  is  a  sealed 
book,  but  the  persevering  energy  of  the  gla- 
cialist  and  archaeologist  is  gradually  turning 
the  leaves  of  this  old  book  and  revealing  new 
chapters  of  the  wonderful  story  of  the  ice. 

As  the  ice  receded  the  arctic  zone  again 
traveled  northward,  and  many  animals,  plants, 
and  trees  that  had  survived  the  vicissitudes  of 
the  ice  age,  traveled  back  with  it.  Some  of 
them,  however,  became  acclimated  and  by 
adapting  themselves  to  the  new  conditions  re- 
mained behind  to  live  and  grow  with  the 
aborigines  of  preglacial  times.  Some  of  the 
plants  and  flowers  that  grew  in  profusion  im- 
mediately under  the  edge  of  the  great  ice  sheet 
were  unable  to  live  under  the  new  conditions 
of  increased  warmth — that  came  with  the 
retrograde  movement  of  the  ice — and  either 
had  to  follow  closely  the  receding  ice  or  escape 
to  higher  altitudes,  where  they  found  a  con- 
genial clime.  Thus  it  is  that  we  have  arctic 
plants  and  flowers  above  the  timber  line  and 
near  the  snow  line  of  our  high  mountains.  In 
proof  of  this  theory  it  has  been  found  that 
these  arctic  plants  do  not  exist  upon  high 
mountains,  such  as  the  Peak  of  Teneriffe, 
where  they  have  been  isolated  from  the  gla- 
ciated region.  The  Peak  of  Teneriffe  is  situ- 
ated on  one  of  the  Canary  Islands,  surrounded 
by  water,  so  that  there  was  no  possible  chance 


238  matured  Miracles 

for  the  arctic  plants  to  seek  refuge  on  these 
isolated  elevations,  such  as  the  continental 
mountains  furnish. 

Thus  it  will  be  seen  that  the  progression  and 
recession  of  the  ice  have  not  only  formed  great 
lakes,  changed  river  beds,  and  covered  a  mil- 
lion square  miles  of  area  with  glacial  drift 
averaging  fifty  feet  in  depth,  making  many 
waterfalls  and  giving  variety  to  the  surface  of 
the  earth,  besides  producing  the  finest  agri- 
cultural region  in  the  world,  but  have  also 
given  variety  to  our  forests  and  plants  wher- 
ever this  ice  sheet  has  extended. 


CHAPTEE  XXIX. 

DRAINAGE    BEFORE    THE    ICE   AGE. 

We  have  already  said  that  during  the  ice 
age  river-beds  were  changed,  valleys  were  filled 
up,  new  lakes  were  made,  and  waterfalls 
created.  Great  as  were  the  changes  made  by 
the  carrying  power  of  moving  ice,  still  greater 
were  those  made  in  preglacial  times ;  not,  how- 
ever, from  the  action  of  moving  ice,  but  from 
running  water.  Erosion  caused  by  running 
water  has,  probably,  during  the  life  of  the 
world,  transported  more  material  from  place 
to  place,  from  mountain  to  valley,  and  from 
valley  to  ocean,  than  any  other  agency ;  chiefly 
for  the  reason  that  it  has  been  so  much  longer 
doing  its  work. 

The  valley  of  the  Ohio  River,  a  thousand 
miles  or  more  in  length,  together  with  the 
great  number  of  feeders  that  empty  into  it,  is 
an  instance  of  the  wonderful  erosive  power  of 
running  water.  The  valley  of  the  Ohio  River 
will  probably  average  a  mile  in  width  at  its 
upper  level  and,  deep  as  it  is  to-day,  it  was 
much  deeper  in  preglacial  times.  There  is 
evidence  that  the  whole  bed  of  the  river  was 
from  100  to  150  feet  deeper  than  it  is  at  pres- 


240  1ftature'0  .fllMraclee, 

ent.  This  has  been  determined  by  borings  at 
different  points  to  ascertain  the  depth  of  the 
drift  that  was  lodged  during  the  glacial  period 
in  the  trough  of  the  Ohio  River.  Anyone 
traveling  up  or  down  the  river  to-day  can 
readily  see  that  it  is  a  great  sinuous  groove 
cut  down  through  the  earth  by  millions  of 
years  of  water  erosion,  and  not  only  this,  but 
that  at  some  time  in  its  history  this  great 
valley  has  been  partly  filled,  forming  on  one 
or  both  sides  of  the  river  level  areas — called 
bottom  land.  These  lands  are  exceedingly 
productive,  owing  to  the  great  depth  and  rich- 
ness of  the  soil. 

For  many  years  the  writer  lived  upon  one  of 
the  rivers  tributary  to  the  Ohio  and  often 
made  trips  by  steamboat  up  and  down  the 
Ohio  River.  Traveling  along  this  river  a 
close  observer  will  be  struck  by  the  exactness 
of  the  stratifications  in  the  rock  and  in  the 
coal  beds  to  be  seen  on  each  side  of  the  river. 
They  match  as  perfectly  as  the  grain  of  a 
block  of  wood  when  sawn  asunder — showing 
that  these  coal  beds  were  formed  at  an  age 
long  before  the  water  cut  this  sinuous  groove. 
What  the  water  was  doing  while  these  coal 
beds  were  forming  will  be  brought  out  in  some 
future  chapter.  All  the  rivers  that  are  tribu- 
tary to  the  Ohio,  such  as  the  Monongahela,  the 
Alleghany,  the  Muskingum,  the  Tennessee,  the 
Cumberland,  the  Kentucky,  the  Wabash,  the 


Drainage  before  tbe  1fce  Bge,      241 

Miami,  the  Licking,  the  Scioto,  the  Big 
Sandy,  the  Kanawha,  the  Hocking,  and  the 
Great  Beaver,  besides  numerous  smaller 
streams,  have  their  own  valleys  that  have  been 
worn  away  by  the  same  process,  and  to  a 
greater  depth  than  they  now  appear  to  be. 
All  of  the  material  that  once  filled  these  val- 
leys has  been  carried  down  by  the  water  filling 
up  the  bottom  of  the  ocean  and  building  out 
the  great  delta  of  the  lower  Mississippi. 
Mountains  have  been  worn  down  and  carried 
away  by  the  action  of  the  running  water  until 
their  height  is  much  lower  than  in  former 
times.  The  great  lakes,  that  were  enlarged 
during  the  glacial  period  and  in  some  cases 
wholly  created — by  the  scooping  out  and  dam- 
ming up  of  the  waterways  and  by  piling  gla- 
cial drift  around  their  shores — have  had  some 
of  their  outlets  raised  to  a  higher  level,  and 
others  have  been  created  anew. 

The  old  river  beds  that  formerly  carrieH  the 
water  that  is  now  drained  through  the  St. 
Lawrence  were  eroded  by  the  action  of  run- 
ning water  to  a  great  depth,  as  is  shown  by 
numerous  borings  along  the  valley  of  the  Mo- 
hawk and  down  the  Hudson.  The  salt  wells 
at  Syracuse,  N".  Y.,  have  been  put  down 
through  glacial  drifts  and  the  salt  water  is 
found  in  the  bed  of  the  old  river.  Great 
bodies  of  salt  are  found  at  that  low  level,  con- 
stantly dissolved  by  the  water  percolating 


242  flatuve's 

through  the  sand  and  gravel  of  the  glacial 
drift.  This  salt  water  is  pumped  up  and  evap- 
orated, leaving  the  salt — forming  one  of  the 
important  industries  of  that  region.  All  of 
the  rivers  from  the  Ohio  eastward  tell  the  same 
story,  which  is  that  at  some  remote  period  the 
land  was  much  higher  above  the  level  of  the 
sea  than  it  is  to-day.  The  bottoms  of  many 
of  these  old  river  beds  are  lower  than  sea-level, 
but  as  they  were  made  by  running  water  they 
must  have  been  at  one  time  above  that  point. 

There  is  abundant  evidence  that  the  earth 
sinks  in  some  places  and  rises  in  others. 
Along  the  ridges  of  some  of  the  eastern  moun- 
tains are  found  in  great  abundance  the 
products  of  the  bottom  of  the  ocean.  These 
evidences  show  that  at  some  period,  when  the 
mountains  were  formed,  a  great  convulsion  of 
nature  raised  the  bottom  of  the  ocean  to  thou- 
sands of  feet  above  its  level.  Evidences  of 
this  exist  in  various  parts  not  only  of  the 
United  States,  but  of  the  world. 

You  ask,  If  this  erosion  goes  on  and  the 
mountains  and  hills  are  carried  down  and 
filled  in  to  the  low  places  of  the  ocean,  what  is 
the  final  destiny  of  the  earth  that  now  appears 
above  the  surface  of  the  ocean?  Evidently  if 
the  earth  should  remain  without  further  up- 
heaval, at  some  time  in  the  far,  far  future  the 
land  would  gradually  wear  down  and  be 
carried  off  into  the  ocean  and  the  ocean  would 


Drainage  before  tbe  1Tce  Bge.      243 

gradually  rise,  owing  to  its  restricted  area, 
until  it  would  again  cover  the  whole  earth  as 
it  undoubtedly  did  at  one  time  in  the  earth's 
history.  This  fact  need  not  occasion  any  un- 
easiness on  the  part  of  those  who  are  living 
to-day  or  for  millions  of  years  to  come. 

The  problem  of  building  a  world  and  then 
tearing  it  to  pieces  is  a  very  complicated  one. 
There  is  a  constant  battle  going  on  between 
the  powers  that  build  up  and  those  that  tear 
down;  and  this  is  as  true  of  character-build- 
ing as  it  is  of  world-building.  The  world  has 
never  been  exactly  alike  any  two  successive 
days  from  the  time  its  foundations  were  laid 
to  the  present  moment.  It  seems  to  be  a  fun- 
damental law  of  all  life  and  growth,  as  well  as 
of  all  decay,  that  there  shall  be  a  constant 
change.  There  is  no  such  thing  as  rest  in 
nature.  The  smallest  molecules  and  atoms  of 
matter  are  in  constant  agitation.  In  the  ani- 
mal and  vegetable  world  there  is  a  period  of 
life  and  growth,  and  a  period  of  decay  and 
death;  and  this  seems  to  be  the  destiny  of 
planets  themselves  as  well  as  the  things  that 
live  and  grow  upon  them.  Still,  science 
teaches  us  that  with  all  this  turmoil  and 
change  nothing  either  of  matter  or  energy  is 
lost,  but  that  it  is  simply  undergoing  one  eter- 
nal round  of  change.  Does  this  law  apply  to 
mind  and  soul?  Do  we  die?  Or  do  we 
simply  change? 


Nature's  fllMrades: 

FAMILIAR   TALKS    ON    SCIENCE. 

By  PROF.  ELISHA  GRAY. 


VOL.  I-Wotto  Glutting  an&  Xife : 

jEattb,  Bfr,  ant>  1C\atcv. 

VOL.  ii.  —  j£ner0B  an&  Dibration : 

fforce,  Ibeat,  %tgbt,  Sounb,  J6n>losfv>es. 

VOL.  in.— ElectrfcftB  an&  flfcagnettem. 


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college  course ;  his  genius  interested  him  in  electricity, 
and  in  that  realm  his  Inventions  have  made  him  famous. 
These,  with  his  organization  and  presidency  of  the  Con- 
gress of  Electricians  at  the  Columbian  Fair  of  1893,  and  his 
many  decorations  and  degrees,  conferred  at  home  and 
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has  been  won  not  by  catering  to  the  applause  of  the  pub- 
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